Faculty Profiles - TODA Kenji

Papers - TODA Kenji

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Blue-yellow multicolor phosphor, Eu2+-activated Li3NaSiO4: Excellent thermal stability and quenching mechanism Reviewed

Masato Iwaki, Shota Kumagai, Shoma Konishi, Atsuya Koizumi, Takuya Hasegawa, Kazuyoshi Uematsu, Atsushi Itadani, Kenji Toda, Mineo Sato

Journal of Alloys and Compounds 2018.10

Novel and Incredibly Facile Low Temperature Solid State Route to Nano-Sized Eu3+ Activated BaTiO3 Phosphors Reviewed

Usama Bin Humayoun, Sintayehu Nibret Tiruneh, Yung-Hyun Song, Takaki Masaki, Kenji Toda, Dae-Ho Yoon

Science of Advanced Materials 10 ( 9 ) 1225 - 1229 2018.9

Room-Temperature Solid State Contact Reaction Synthesis of Rare Earth Free RbVO3 Phosphor and Their Photoluminescence Properties Reviewed

Tadashi Ishigaki, Puttaswamy Madhusudan, Shinnosuke Kamei, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

ECS Journal of Solid State Science and Technology 7 ( 6 ) R88 - R93 2018.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELECTROCHEMICAL SOC INC

Rare earth free RbVO3 ceramic materials were prepared by facile solid-solid contact reaction between Rb2CO3 and V2O5 powders at room temperature within few minutes. Synchrotron X-ray power diffraction analysis and energy dispersive X-ray spectroscopy study showed that the resultant nanoparticles are crystalline with almost 100% purity. Further, the as-prepared sample showed emission spectrum intensity at 530 nm implying that RbVO3 ceramic materials can be used for white LED application. In addition, when 0.01 M aqueous NH4OH was added to the mixture of Rb2CO3 and V2O5, the emission intensity of the product was about twice higher than that of the product obtained from the reaction in moist air. The luminescence internal quantum efficiency (QE) of as-prepared RbVO3 phosphor is about 35% as estimated by a direct method. The present room-temperature fabrication method has great potential in large-scale fabrication of phosphor materials as well as other composite functional materials due to significantly reduced reaction time and energy. (C) 2018 The Electrochemical Society.

DOI： 10.1149/2.0201806jss

Luminescence enhancement of LiSrPO4:Eu2+ phosphor by Mg2+ ion addition Reviewed

Kamei Shinnosuke, Tomoki Hatsumori, Takuya Hasegawa, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

Materials Research Innovations 2018.6

Synthesis of High-Efficiency Red-Emission Ca14Zn6Al9.97Mn0.03O35 Phosphors with Particle Control Reviewed

Man Gyu Hur, Seung Hee Choi, Seok Bin Kwon, Takaki Masaki, Kenji Toda, Dae Ho Yoon

Ceramics International 44 15868 - 15872 2018.6

Synthesis of Na<inf>2</inf>FePO<inf>4</inf>F using polytetrafluoroethylene Reviewed

Atsushi Tsu-Ura, Hirotaka Torii, Takuya Hasegawa, Dai Murayama, Sun Woog Kim, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

Journal of the Ceramic Society of Japan 126 ( 5 ) 336 - 340 2018.5

Language：English Publishing type：Research paper (scientific journal)

© 2018 The Ceramic Society of Japan. All rights reserved. Polytetrafluoroethylene (PTFE), composed of fluorine and carbon atoms, has a potential to produce carbon-coated fluorides in the calcination of inorganic compounds. We synthesized high voltage cathode material for Na ion secondary battery, Na2FePO4F, using PTFE as the carbon-coating and fluorine source. The Na2FePO4F carbon-coated by a thermal decomposition of PTFE showed high discharge capacity (64.4 mAh g11) at the first cycle of galvanostatic cycling by the improvement of conductivity.

DOI： 10.2109/jcersj2.17230

Paradigm Change for Solid State Reactions: Synthesis of Lithium Orthophosphate Li3PO4 Nanoparticles by a Water Assisted Solid State Reaction (WASSR) Method Reviewed

Sun Woog Kim, Kenji Toda, Takuya Hasegawa, Mizuki Watanabe, Tatsuro Kaneko, Ayano Toda, Atsushi Itadani, Mineo Sato, Kazuyoshi Uematsu, Tadashi Ishigaki, Junko Koide, Masako Toda, Yoshiaki Kudo, Takaki Masaki, Dae Ho Yoon

Science of Advanced Materials 10 ( 4 ) 592 - 596 2018.4

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER SCIENTIFIC PUBLISHERS

Lithium orthophosphate Li3PO4 nanoparticles were synthesized through a water assisted solid state reaction (WASSR) method. The nanoparticles obtained in this study adopt a stable orthorhombic structure (beta-type), which is a low temperature phase, in a single phase with high crystallinity. The Li3PO4 nanoparticles have a granular particle morphology and the particle size is less than 50 nm.

DOI： 10.1166/sam.2018.2844

Structure of triaquatris(1,1,1-trifluoro-4-oxo-pentan-2-olato)cerium(III) as a possible fluorescent compound Reviewed

Atsuya Koizumi, Takuya Hasegawa, Atsushi Itadani, Kenji Toda, Taoyun Zhu, Mineo Sato

Acta Crystallographica Section E: Crystallographic Communications 74 229 - 232 2018.2

Language：English Publishing type：Research paper (scientific journal)

© 2018 International Union of Crystallography. Luminescence due to the d-f transition of Ce3+ is quite rare in metal-organic complexes where concentrate quenching frequently occurs. One of the possible ways to avoid this is to design an architecture with elongated metal-metal distances. In the structure of the title complex, triaquatris(1,1,1-trifluoro-4-oxopentan-2-olato-2O,O0)cerium(III), [Ce(C5H4F3O2)3(H2O)3], the CeIII complex is linked to neighbouring ones by hydrogen bonding. Within the complex, the CeIII atom is coordinated by nine O atoms from three 1,1,1-trifluoro-4-oxopentan-2-olate (tfa) anions as bidentate ligands and three water molecules as monodentate ligands. Thus, the coordination number of CeIII atom is nine in a monocapped square-antiprismatic polyhedron. The F atoms of all three independent CF3 groups in tfa are disordered over two positions with occupancy ratios of about 0.8:0.2. The intermolecular hydrogen bonds between the ligands involve tfa-water interactions along the [110] and [110] directions, generating an overall two-dimensional layered network structure. The presence of the F atoms in the tfa anion is responsible for an increased intermolecular metal-metal distance compared to that in the analogous acetylacetonate (acac) derivatives. Fluorescence from Ce3+ is, however, not observed.

DOI： 10.1107/S2056989018001135

Synthesis of nano-sized materials using novel water assisted solid state reaction method Reviewed

Kenji Toda, Tatsuro Kaneko, Takuya Hasegawa, Mizuki Watanabe, Yusuke Abe, Takeshi Kuroi, Mineo Sato, Kazuyoshi Uematsu, Sun Woog Kim, Yoshiaki Kudo, Takaki Masaki, Dae Ho Yoon

Key Engineering Materials 777 KEM 163 - 167 2018

Language：English Publishing type：Research paper (international conference proceedings)

© 2018 Trans Tech Publications, Switzerland. We report synthesis of nano-sized oxide materials using a novel water assisted solid state reaction (WASSR) method. This novel soft chemical synthesis method is very simple and can synthesize nanoparticle materials just by storing or mixing raw materials added a small amount (typically 10wt%) of water in a reactor at low temperature below 373 K. Combinations of raw materials have a significant influence on the reaction rate.

DOI： 10.4028/www.scientific.net/KEM.777.163

Luminescence property of silicate phosphor, Ba9Sc2Si6O24:Ce, synthesized by melt quenching technique Reviewed

Kenji Toda, Atsushi Tsu-Ura, Minenori Katsu, Shin-Nosuke Kamei, Tadashi Ishigaki, Kazuyoshi Uematsu, Mineo Sato

Key Engineering Materials 766 186 - 190 2018

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Trans Tech Publications Ltd

Well-grown Ba9Sc2Si6O24:Ce3+ phosphors were synthesized by a novel melt quenching synthesis method. Sintered phosphor balls with excellent luminescent characteristics were obtained. This method is useful tool for rapid screening of phosphor materials.

DOI： 10.4028/www.scientific.net/KEM.766.186

Bluish-White Luminescence in Rare-Earth-Free Vanadate Garnet Phosphors: Structural Characterization of LiCa3MV3O12 (M = Zn and Mg) Reviewed

Takuya Hasegawa, Yusuke Abe, Atsuya Koizumi, Tadaharu Ueda, Kenji Toda, Mineo Sato

Inorganic Chemistry 57 ( 2 ) 857 - 866 2017.12

Nanophosphors synthesized by the water assisted solid state reaction (WASSR) method: Luminescence properties and reaction mechanism of the WASSR method Reviewed

Sun Woog Kim, Takuya Hasegawa, Mizuki Watanabe, Masaru Muto, Toshiya Terashima, Yusuke Abe, Tatsuro Kaneko, Ayano Toda, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato, Emiko Kawakami, Junko Koide, Masako Toda, Yoshiaki Kudo, Takaki Masaki, Dae Ho Yoon

Applied Spectroscopy Reviews 52 ( 10 ) 1 - 18 2017.10

Yellow MgV2O6 center dot 2H(2)O nanophosphor synthesized by a water-assisted solid-state reaction (WASSR) method at low temperature below 80 degrees C Reviewed

Sun Woog Kim, Yusuke Abe, Mizuki Watanabe, Takuya Hasegawa, Masaru Muto, Ayano Toda, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato, Emiko Kawakami, Junko Koide, Masako Toda, Yoshiaki Kudo, Toshiyuki Masui, Takaki Masaki, Dae Ho Yoon

DYES AND PIGMENTS 145 339 - 344 2017.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Magnesium metavanadate dihydrate (MgV2O6.2H(2)O) was synthesized as a nanophosphor by a water assisted solid-state reaction (WASSR) method, and its crystal structure and luminescence properties were investigated in detail. MgV2O6.2H(2)O has an orthorhombic structure with space group Pnma. In the crystal structure, the MgO6 octahedra and VO4 tetrahedra formed a layered structure in the direction of the b axis, and the VO4 tetrahedra formed a chain structure along the a axis. The nanophosphor showed broad and strong optical absorption in the near-ultraviolet region and exhibited a broad yellow emission peak at 563 nm. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dyepig.2017.06.024

Synthesis and optical properties of P 5+ co-doped Ba 3 SiO 5 :Eu 2+ orange persistent phosphor Reviewed

Seung Hee Choi, Seok Bin Kwon, Usama Bin Humayoun, Won Kyu Park, Kenji Toda, Masato Kakihana, Takaki Masaki, Woo Seok Yang, Young Hyun Song, Dae Ho Yoon

Dyes and Pigments 148 460 - 464 2017.9

Stabilization of novel high temperature phase yellow-emitting σ-type (Ba<inf>1-: X - Y</inf>Eu<inf>x</inf>Mg<inf>y</inf>)<inf>2</inf>P<inf>2</inf>O<inf>7</inf> phosphors using a melt synthesis technique Reviewed

H. Nakagawa, S. W. Kim, T. Hasegawa, S. Hasegawa, T. Ishigaki, K. Uematsu, K. Toda, H. Takaba, M. Sato

Inorganic Chemistry Frontiers 4 ( 9 ) 1562 - 1567 2017.9

Language：English Publishing type：Research paper (scientific journal)

© 2017 the Partner Organisations. Novel Eu2+-activated phosphate phosphors based on high-temperature phase σ-Ba2P2O7, which is an unstable phase at room temperature, were synthesized for the first time by a melt synthesis technique using an arc-imaging furnace. By doping Mg2+ into the host lattice, Eu2+-activated σ-Ba2P2O7 phosphors were successfully obtained in a single phase form of a hexagonal structure and the emission intensity was also effectively enhanced. The relative emission peak intensity of the σ-(Ba0.67Eu0.03Mg0.30)2P2O7 phosphor was 315% of that for the σ-(Ba0.97Eu0.03)2P2O7 phosphor. The emission color tunable from green emission with a peak at 516 nm to yellow emission with a peak at 551 nm can be achieved by controlling the Mg2+ content in the σ-(Ba0.97-yEu0.03Mgy)2P2O7 phosphors.

DOI： 10.1039/c7qi00359e

Unusual, broad red emission of novel Ce3+ -activated Sr3Sc4O9 phosphors under visible-light excitation Reviewed

Takuya Hasegawa, Sun Woog Kim, Tadaharu Ueda, Tadashi Ishigaki, Kazuyoshi Uematsu, Hiromitsu Takaba, Kenji Toda, Mineo Sato

JOURNAL OF MATERIALS CHEMISTRY C 5 ( 36 ) 9472 - 9478 2017.9

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Most conventional white light emitting diodes (white-LEDs) that are widely used as a new lighting system in next generation lights with Y3Al5O12: Ce3+ (YAG: Ce3+)-based phosphors have a low colour rendering index (CRI) because the YAG: Ce3+ phosphor shows a weak emission intensity in the red spectral region. Therefore, discovering a red-emitting phosphor with a high-efficiency is quite important to enhance the CRI of white-LEDs. In this study, we successfully discovered a novel, red-emitting Ce3+-activated Sr3Sc4O9 phosphor that can be excited by blue-light irradiation at 425 nm. A crystal structure of the host material was first determined by Rietveld refinement, which indicated that it should be isostructural with Ba(3)Ln(4)O(9) (Ln = Sc, Y and Dy-Lu). As the Ce3+ content increased, the X-ray diffraction patterns shifted to a lower angle, which suggested that the Ce3+ ion could substitute Sc in the Sr3Sc4O9 host. Under UV and blue-light excitation, the Ce3+-activated Sr3Sc4O9 phosphor exhibited a broad emission band with a maximum peak at 620 nm, and its full width half maximum (FWHM) was 180 nm (4530 cm(-1)). The highest emission intensity was obtained for Sr-3(Sc0.997Ce0.003)(4)O-9, and the internal quantum efficiency of this phosphor under excitation at 425 nm was 53%. To the best of our knowledge, the emission band of the Ce3+-activated Sr3Sc4O9 phosphor is the longest wavelength for a reported Ce3+-activated oxide phosphor.

DOI： 10.1039/c7tc03203j

Exquisite morphology, highly emissive yellow Sr1.44Ba0.46SiO4:0.1Eu(2+) phosphor synthesized by a liquid phase precursor process Reviewed

Usama Bin Humayoun, Young Hyun Song, Seok Bin Kwon, Kakihana Masato, Kenji Toda, Yasushi Sato, Takaki Masaki, Dae-Ho Yoon

DYES AND PIGMENTS 142 147 - 152 2017.7

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Yellow phosphors are the major components of contemporary solid-state lights. YAG:Ce3+ is a widely adopted yellow phosphor component; however, it too has limitations. Here, we report the synthesis and application of a very highly efficient yellow-emitting orthosilicate phosphor. Yellow-emitting Sr1.44Ba0.46SiO4:0.1Eu(2+) was synthesized by an unconventional cellulose template liquid phase precursor process (CTLPP). The naturally abundant and nonhazardous cellulose template facilitates efficient synthesis at lower temperatures. The synthesized phosphor was indexed to alpha-Sr2SiO4 phase and exhibited broad excitation and broad emission with a peak at 545 nm, very high intensity, almost 130% of commercial YAG upon excitation at 450 nm. The morphology of the phosphors was also nearly spherical, which also enables their use in WLEDs. Use of non-stoichiometric Si precursors (i.e. Sr1.44Ba0.46SixO4:0.1Eu(2+), x = 0.95, 1.0 and 1.05) in the process resulted in remarkable effects on the morphology (size and surface) and luminescent characteristics and exceptional quantum efficiencies of the phosphors. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dyepig.2017.03.029

Improvement of luminescence properties of rubidium vanadate, RbVO3, phosphors by erbium doping in the crystal lattice Reviewed

S. W. Kim, T. Hasegawa, M. Muto, A. Toda, T. Kaneko, K. Sugimoto, K. Uematsu, T. Ishigaki, K. Toda, M. Sato, J. Koide, M. Toda, Y. Kudo

NEW JOURNAL OF CHEMISTRY 41 ( 12 ) 4788 - 4792 2017.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Greenish-white emitting Rb1-xErxVO3 (0 <= x <= 0.10) phosphors were synthesized by a conventional solid state reaction method. The thermal quenching effect of the RbVO3 phosphors was effectively improved by Er3+ doping into the RbVO3 lattice. Consequently, the emission peak intensity of the phosphors was successfully enhanced by Er3+ doping, and the internal quantum efficiency of Rb0.99Er0.01VO3 under excitation at 360 nm was 80%.

DOI： 10.1039/c6nj03823a

On the possibility of polystyrene-derived carbon coating for NASICON-type Na3V2(PO4)(3) composites as cathode materials for sodium-ion batteries Reviewed

Dai Okada, Takumi Fugane, Yuka Matsumoto, Takuya Hasegawa, Atsushi Itadani, Kazuyoshi Uematsu, Kenji Toda, Hideki Hashimoto, Jun Takada, Mineo Sato

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 125 ( 4 ) 322 - 325 2017.4

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

We here prepared polystyrene-derived carbon-coated Na3V2(PO4)(3) composite (NVP/C) cathode materials via a solid-phase reaction using a mixture of NVP precursor and polystyrene (as the carbon source), followed by calcination at high temperatures. Using this method, we were able to obtain active NVP materials with relatively high purity while allowing a uniform surface coating with carbon layers about 3-4 nm thick. This structure significantly prevented NVP particle growth even after calcination at high temperatures. The NVP/C material calcined at 700 degrees C exhibited the best charge-discharge performance among the samples studied. (C) 2017 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.16266

Discovery of novel inorganic Mn5+-doped sky-blue pigments based on Ca6BaP4O17: Crystal structure, optical and color properties, and color durability Reviewed

Sun Woog Kim, Go Eun Sim, Ji Young Ock, Jeong Hun Son, Takuya Hasegawa, Kenji Toda, Dong Sik Bae

DYES AND PIGMENTS 139 344 - 348 2017.4

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Novel inorganic sky-blue pigments, Ca6Ba(P1-xMnx)4O(17) (0 <= x <= 0.13) were synthesized in a single phase form by a conventional solid-state reaction method and their color properties were investigated in the detail. The pigments exhibited strong optical absorption in the UV and the yellow-red light regions due to the cT transition in MnO4 tetrahedra and the DMSO-d(6) transitions of Mn5+, which is the origin of the sky-blue color. The optimization of the composition resulted in the attainment of the highest sky-blue hue for the Ca6Ba(P0.99Mn0.01)4O(17), where the L*, a*, b*, C, and H values are 75.47, -11.67, -10.29, 15:6, and 221.4 degrees, respectively. These pigments showed a low chemical stability of color for acid/alkali solution, whereas the pigments showed an excellent color durability for heat and light. Although they are required to improve the chemical stability of color, the present pigment could be an attractive candidate as a novel environment friendly inorganic sky-blue pigment.(C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dyepig.2016.12.038

Development of a novel nontoxic vivid violet inorganic pigment - Mn3+-doped LaAlGe2O7 Reviewed

Sun Woog Kim, Yu Saito, Takuya Hasegawa, Kenji Toda, Kazuyoshi Uematsu, Mineo Sato

DYES AND PIGMENTS 136 243 - 247 2017.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Novel nontoxic LaAl1-xMnxGe2O7 (0.01 <= x <= 0.20) violet pigments were synthesized through a conventional solid-state reaction. The crystal structures, optical properties, and color properties of these pigments were investigated. The LaAl1-xMnxGe2O7 (0.01 <= x <= 0.20) pigments prepared in the present study show excellent potential as environmentally friendly inorganic violet pigments. These pigments exhibit a strong optical absorption in the yellow-red light region due to the Mn3+ d-d transitions, which is the origin of the violet color. Among the obtained LaAl1-xMnxGe2O7 (0.01 <= x <= 0.20) pigments, LaAl0.90Mn0.10Ge2O7 showed the most vivid violet color and the L*, a*, and b* values are 50.8, 18.0, and -29.7, respectively, values greater than those of a commercial cobalt violet pigment (Co-3(PO4)(2); L* = 46, a* = 33, b* = 32). Because the LaAl0.90Mn0.10Ge2O7 pigment is composed of nontoxic elements, this pigment can be an effective alternative to currently used commercial violet pigments. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dyepig.2016.08.038

Environmentally friendly Rb3V5O14 fluorescent red pigment Reviewed

Sun Woog Kim, Takuya Hasegawa, Mizuki Watanabe, Kazuma Sugimoto, Yu Saito, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

DYES AND PIGMENTS 136 219 - 223 2017.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Rb3V5O14, which was successfully synthesized by a water assisted solid state reaction (WASSR) method, is a fluorescent red pigment that is environmentally friendly. The Rb3V5O14 fluorescent pigment showed a strong optical absorption in the green light region due to the energy transfer from O2- 2p orbital to V5+ 3d orbital of VO5 polyhedra and band-gap energy of Rb3V5O14 was 2.02 eV. The fluorescent pigment presented a broad red emission peaked at 625 nm due to the T-3(2) -> (1)A(1) and T-3(1) -> (1)A(1) transitions of the [VO4](3-) group. The Rb3V5O14 fluorescent pigment showed a bright-vivid red body color, and the L*, a*, and b* values were 47.4, +45.9, and +34.4, respectively. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dyepig.2016.08.040

Luminescence of phosphor balls prepared using melt quenching synthesis method Reviewed

Takuya Hasegawa, Kenji Toda, Tadashi Ishigaki, Shinnosuke Kamei, Sun Woog Kim, Kazuyoshi Uematsu, Mineo Sato, Masahiro Yoshimura

Materials Science Forum 883 17 - 21 2017

Language：English Publishing type：Research paper (international conference proceedings)

© 2017 Trans Tech Publications, Switzerland. Well-grown M3MgSi2O8 (M = Ca, Sr and Ba):Eu2+ phosphors were synthesized by novel melt quenching synthesis method. The luminescence property of the Sr3MgSi2O8:Eu2+ phosphor synthesized by the melt synthesis method is comparable to those of the sample synthesized by a conventional solid state reaction. Sintered phosphor balls with excellent luminescent characteristics were obtained.

DOI： 10.4028/www.scientific.net/MSF.883.17

Synthesis of Li2SiO3 using novel water-assisted solid state reaction method Reviewed

Mizuki Watanabe, Jun Inoi, Sun Woog Kim, Tatsuro Kaneko, Ayano Toda, Mineo Sato, Kazuyoshi Uematsu, Kenji Toda, Junko Koide, Masako Toda, Emiko Kawakami, Yoshiaki Kudo, Takaki Masaki, Dae Ho Yoon

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 125 ( 6 ) 472 - 475 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Single phase of orthorhombic Li2SiO3 was synthesized via a novel soft-chemical synthesis method, water assisted solid state reaction method at 343-353K for 60 min. The crystal structure of the samples was characterized by X-ray diffraction (XRD) analysis. The scanning electron microscope (SEM) observation revealed that the estimated size of the particles is 50-200 nm. The XRD patterns and SEM images were compared to those of samples by a conventional solid state method at 1173K for 4 h. (C) 2017 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.16325

Determination of the crystal structure and photoluminescence properties of NaEu1-xGdx(MoO4)(2) phosphor synthesized by a water-assisted low-temperature synthesis technique Reviewed

Takuya Hasegawa, Sun Woog Kim, Yusuke Abe, Masaru Muto, Mizuki Watanabe, Tatsuro Kaneko, Kazuyoshi Uematsu, Tadashi Ishigaki, Kenji Toda, Mineo Sato, Junko Koide, Masako Toda, Yoshiaki Kudo

RSC ADVANCES 7 ( 40 ) 25089 - 25094 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

A single-phase red-emitting NaEu(MoO4)(2) phosphor with nanosized particles was synthesized using a water-assisted solid state reaction (WASSR) method, a new low-temperature synthesis method developed by our group. NaEu(MoO4)(2) exhibits a monoclinic structure with a space group C2/c (no. 15), which is composed of a Na/EuO8 dodecahedron with the site occupancy of Na/Eu = 1 : 1 and an MoO4 tetrahedron. To enhance the emission intensity of the NaEu(MoO4)(2) phosphor, Gd3+ was doped into the Eu3+ sites and NaEu1-xGdx(MoO4)(2) (0 < x <= 0.50) samples were synthesized using the WASSR method. The emission intensity of the phosphors was successfully enhanced by increasing the Gd3+ content in the samples with 0 <= x <= 0.30, but was reduced with x > 0.30. This indicates that the optimum composition of the phosphor for achieving a high emission intensity that is similar to 3.8 times higher than that of the NaEu(MoO4)(2) (x = 0) phosphor is NaEu0.70Gd0.30(MoO4)(2). These phosphors exhibit a granular particle morphology with the particle size of the phosphor being similar to 200 nm.

DOI： 10.1039/c7ra01832k

A new lanthanum(III) complex containing acetylacetone and 1 H -imidazole Reviewed

Atsuya Koizumi, Takuya Hasegawa, Atsushi Itadani, Kenji Toda, Taoyun Zhu, Mineo Sato

Acta Crystallographica Section E: Crystallographic Communications 73 1739 - 1742 2017

Language：English Publishing type：Research paper (scientific journal)

© Koizumi et al. 2017. In the title complex, diaqua(1H-imidazole-κN 3)(nitrato-κ 2 O,O′)bis(4-oxopent-2-en-2-olato-κ 2 O,O′)lanthanum(III), [La(C 5 H 7 O 2) 2 (NO 3)(C 3 H 4 N 2)(H 2 O) 2 ], the La atom is coordinated by eight O atoms of two acetylacetonate (acac) anions acting as bidentate ligands, two water molecule as monodentate ligands, one nitrate anions as a bidentate ligand and one N atom of an imidazolate (ImH) molecule as a monodentate ligand. Thus, the coordination number of the La atom is nine in a monocapped square antiprismatic polyhedron. There are three types of intermolecular hydrogen bonds between ligands, the first involving nitrate-water O⋯H - O interactions running along the [001] direction, the second involving acac-water O⋯H - O interactions along the [010] direction and the third involving an Im-nitrate N - H⋯O interaction along the [100] direction (five interactions of this type). Thus, an overall one-dimensional network structure is generated. The molecular plane of an ImH molecule is almost parallel to that of a nitrate ligand, making an angle of only 6.04(12)°. Interestingly, the ImH plane is nearly perpendicular to the planes of two neighbouring acac ligands.

DOI： 10.1107/S205698901701461X

Development of water assisted solid state reaction for the ceramic materials Reviewed

Kenji Toda, Sun Woog Kim, Takuya Hasegawa, Mizuki Watanabe, Tatsuro Kaneko, Ayano Toda, Ryota Yamanashi, Shota Kumagai, Masaru Muto, Atsushi Itadani, Mineo Sato, Kazuyoshi Uematsu, Tadashi Ishigaki, Junko Koide, Masako Toda, Emiko Kawakami, Yoshiaki Kudo, Takaki Masaki, Dae Ho Yoon

Key Engineering Materials 751 KEM 353 - 357 2017

Language：English Publishing type：Research paper (international conference proceedings)

© 2017 Trans Tech Publications, Switzerland. We report a novel soft chemical synthesis method, water assisted solid state reaction (WASSR) method. This method is very simple and can synthesize many ceramic materials just by storing or mixing raw materials added a small amount of water in a reactor at low temperature below 373 K. For example, well-crystalline SrMoO4 was obtained using the WASSR method.

DOI： 10.4028/www.scientific.net/KEM.751.353

Improvement of Emission Intensity for Near-infrared-emitting Ca14Zn6Al10O35:Mn4+ Phosphor by Oxygen-pressure Method Reviewed

Takuya Hasegawa, Sun Woog Kim, Takeshi Abe, Shota Kumagai, Ryota Yamanashi, Kohei Seki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

CHEMISTRY LETTERS 45 ( 9 ) 1096 - 1098 2016.9

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

We employed an oxygen-pressure method as a novel approach to improve the emission intensity of a Ca14Zn6Al10O35:Mn4+ phosphor. With this new approach, the Ca14Zn6Al10O35:Mn4+ phosphor exhibited near-infrared emission under excitation at 450 rim, and the emission intensity of a Caw Zn-6(Al0.97Mn0.03)(10)O-35 phosphor was effectively enhanced by approximately 143% compared with that of a Ca14Zn6(Al0.97Mn0.03)(10)O-35 phosphor synthesized by a conventional solid-state reaction method in air.

DOI： 10.1246/cl.160498

Suppress of Concentration Quenching by Site Engineering Concept Reviewed

Y. Imanari, T. Hasegawa, M. Watanabe, K. Toda, T. Ishigaki, S. Kamei, S. W. Kim, K. Uematsu, M. Sato

Applied Mechanics and Materials 851 132 - 137 2016.8

Synthesis and photoluminescence properties of oxynitride phosphors M0.98Si2O2N2: Eu-0.02(2+) (M=Ba, Sr, Ca) using the cellulose assisted liquid phase precursor process Reviewed

Yelim Song, Younghyun Song, Kenji Toda, Takaki Masaki, Daeho Yoon

CERAMICS INTERNATIONAL 42 ( 8 ) 9667 - 9672 2016.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Oxynitride phosphors M0.98Si2O2N2: Eu-0.02(2+)(M=Ba, Sr, Ca) for white LEDs were synthesized at 1300,1400, and 1500 degrees C by using the partially cellulose assisted liquid phase precursor (PLPP) process and compared with solid state reaction (SSR) process. MSi2O2N2 (M=Ba, Sr, Ca) crystal structure was obtained from M0.98Si2O2N2: Eu-0.02(2+) phosphor fired at 1400 degrees C using the PLPP process. However these phosphors were not synthesized through the SSR process at same temperature. M0.98Si2O2N2: Eu-0.02(2+)(M=Ba, Sr, Ca) phosphors from PLPP produced a blue color emission at 487 nm (380 nm excitation), a green color emission at 528 nm (374 nm excitation), and a yellow color emission at 538 nm (371 nm excitation). M0.98Si2O2N2: Eu-0.02(2+) phosphors from PLPP had higher luminescence and crystallinity compared with those obtained from the SSR process. The prepared phosphors were analyzed by X-ray diffraction (XRD), photoluminescence (PL) and field-emission scanning electron microscopy (FE-SEM). (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

DOI： 10.1016/j.ceramint.2016.03.055

Abnormal improvement in emission of lanthanum oxysulfide phosphor La2O2S:Tb3+ synthesized by a novel method, thermal decomposition in eutectic molten salt Reviewed

Sun Woog Kim, Takuya Hasegawa, Takeshi Abe, Hiroko Nakagawa, Shota Hasegawa, Kohei Seki, Kenji Toda, Kazuyoshi Uematsu, Tadashi Ishigaki, Mineo Sato

CERAMICS INTERNATIONAL 42 ( 8 ) 10389 - 10392 2016.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

The lanthanum oxysulfide phosphor La2O2S:Tb3+ is generally synthesized by the direct sulfidation of La2O3 using H2S or CS2 gas. However, these gases are known to be highly toxic to humans. In this paper, a new synthesis method that uses 0.6U(2)SO(4)-0.4Na(2)SO(4) as the flux is proposed for obtaining La2O2S:Tb3+ phosphor, without the need for H2S or CS2 gas. The proposed method consists of two steps: 1) oxidation to obtain La2O2SO4 and 2) reduction to reduce La2O2SO4 to La2O2S. Using this novel method, (La1-xTbx)(2)O2S (0.01 <x < 0.13) were successfully synthesized in a single-phase form. The synthesized phosphors exhibited extraordinary luminescence behavior. Further, despite their low Tb3+ ion content, the phosphors showed high emission intensities. The relative emission intensity of (La0.95Tb0.05)(2)O2S (lambda(ex) = 270 nm) was 132% that of the commercial green-emitting phosphor (La0.52Ce0.31Tb0.17)PO4 (lambda(ex) = 285 nm), which shows the highest excitation absorption. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

DOI： 10.1016/j.ceramint.2016.03.176

Physical studies on the enhancement of photoluminescence properties for blue BaAl2Si2O8 : Eu2+ phosphors via LPP method with addition of silicate concentrations Reviewed

Bong Sung Kim, Min Ji Lee, Takesi Abe, Takaki Masaki, Young-Hyun Song, Kenji Toda, Dae-Ho Yoon

JOURNAL OF CERAMIC PROCESSING RESEARCH 17 ( 4 ) 286 - 289 2016.4

Language：English Publishing type：Research paper (scientific journal) Publisher：KOREAN ASSOC CRYSTAL GROWTH, INC

BaAl2Si2O8: Eu2+ + xSiO(2) (x = 0, 1, 2 and 3) has been synthesized with phosphors via novel liquid phase precursor (LPP) method. The best crystalline BaAl2Si2O8 : Eu2+ phosphor could not be synthesized as the calcination temperature is inadequate fully to crystalize the phosphor leading to the crystal and amorphous. Albeit, the firing temperature is insufficient so as to form the fine crystal, the added excess SiO2 could act as an additive for the crystallization of the phosphor. As a function of SiO2, the size of the crystal has been augmented and formed fine crystals with the concentration of added SiO2. Moreover, the added excess SiO2 makes SiOC : Eu2+ phosphor as a deep blue illumination at 440 nm. Photoluminescence intensity of the phosphors is increased continuously by the addition of SiO2 heretofore x = 3. In the present investigation, an attempt has been made to synthesize and observe carefully for photoluminescence properties with regard to the crystalline structure, optical property and surface morphology.

Synthesis of high intensity green emitting (Ba,Sr)SiO4:Eu2+ phosphors through cellulose assisted liquid phase precursor process Reviewed

Usama Bin Humayoun, Young-Hyun Song, Minji Lee, Kakihana Masato, Hiroshi Abe, Kenji Toda, Yasushi Sato, Takaki Masaki, Dae-Ho Yoon

OPTICAL MATERIALS 51 110 - 114 2016.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Green emitting phosphor (Ba1-xSr1-x)SiO4:2xEu(2+), x = 0.03, 0.05, 0.1, and 0.15 were synthesized through a Liquid Phase Precursor Process (LPP). Liquid phase precursor method is reported to result in phosphors with markedly increased emission intensities compared to other synthesis methods. Here microcrystalline cellulose (MCC) and hydroxypropyl cellulose (HPC) templates were studied to achieve high efficiency green phosphors. The phase formation was investigated by XRD analysis which showed the conformation of the Ba2SiO4 (JCPDS card number 761631) phase. The obtained samples exhibited broad excitation spectra with maximum at 430 nm and a green emission centered around 520 nm. An optimized dopant concentration was selected and the effect of two different types of cellulose, i.e. MCC and HPC templates on the emission properties was considered. It was found that the samples synthesized using HPC and fired at 1050 degrees C under a reducing atmosphere, showed a high intensity of almost 2 times that of the MCC sample. Further experiments were conducted by varying viscosity, particle weight, and molecular weight of the HPC template. It was found that the green emission from the (Ba,Sr)SiO4:Eu2+ increased with the increase in viscosity and molecular weight of the template. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optmat.2015.11.036

Rare-earth-free white emitting Ba2TiP2O9 phosphor: revealing its crystal structure and photoluminescence properties Reviewed

Takuya Hasegawa, Sun Woog Kim, Shinnosuke Kamei, Tadashi Ishigaki, Kazuyoshi Uematsu, Koutoku Ohmi, Kenji Toda, Mineo Sato

DALTON TRANSACTIONS 45 ( 28 ) 11554 - 11559 2016

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

A high intensity bluish-white emitting Ba2TiP2O9 phosphor was synthesized by a conventional solid-state reaction method and the precise crystal structure was investigated for the first time by Rietveld refinement analysis. Ba2TiP2O9 has a monoclinic crystal structure with a space group C2/c (no. 15), which is built out of PO4 tetrahedra and TiO5 pyramidal polyhedra connected to form a chain structure along the c-axis. The emission of Ba2TiP2O9 is due to a charge transfer transition between Ti4+-O2- in the pyramidal TiO5. The obtained Ba2TiP2O9 was excited efficiently by UV and VUV and displayed a bright bluish-white luminescence.

DOI： 10.1039/c6dt01715k

Improved synthesis of SrLiAl3N4:Eu2+ phosphor using complex nitride raw material Reviewed

S. W. Kim, T. Hasegawa, S. Hasegawa, R. Yamanashi, H. Nakagawa, K. Toda, T. Ishigaki, K. Uematsu, M. Sato

RSC ADVANCES 6 ( 66 ) 61906 - 61908 2016

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Narrow band deep-red emission SrLiAl3N4:Eu2+ phosphor was synthesized using complex nitride Sr3Al2N4 and Li3AlN2 as raw materials. The SrLiAl3N4:Eu2+ phosphor has the oxoplumbate type triclinic structure as the main phase. The phosphor exhibited deep-red emission peaking at 654 nm under excitation at 450 nm and showed an excellent thermal stability on the thermal quenching effect.

DOI： 10.1039/c6ra14107b

Novel yellowish white-emitting Eu<sup>2+</sup>-activated phosphate phosphor based on Rb<inf>2</inf>Ba<inf>3</inf>P<inf>4</inf>O<inf>14</inf> Reviewed

Kazuma Sugimoto, Takuya Hasegawa, Sunwoog Kim, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

Journal of Ceramic Processing Research 17 ( 5 ) 401 - 404 2016

Language：English Publishing type：Research paper (scientific journal)

© 2016, Hanyang University. All rights reserved. Eu2+-doped Rb2Ba3P4O14 phosphors were synthesized in a single phase form by a conventional solid state reaction method and their optical properties were characterized. These phosphors showed broad optical absorption bands that can cover the UV and near-UV region, and exhibited a narrow deep-blue emission and broad reddish-yellow emission with peaks at 423 nm and 550 nm, respectively. The highest reddish-yellow emission intensity was obtained for Rb2(Ba0.99Eu0.01)3P4O14.

Novel soft chemical synthesis methods of ceramic materials Reviewed

Kenji Toda, Sun Woog Kim, Takuya Hasegawa, Mizuki Watanabe, Tatsuro Kaneko, Ayano Toda, Atsushi Itadani, Mineo Sato, Kazuyoshi Uematsu, Tadashi Ishigaki, Junko Koide, Masako Toda, Yoshiaki Kudo, Takaki Masaki, Dae Ho Yoon

Key Engineering Materials 690 268 - 271 2016

Language：English Publishing type：Research paper (international conference proceedings)

© 2016 Trans Tech Publications, Switzerland. We report novel soft chemical synthesis method, solid hydratethermal reaction (SHR) method as a new soft chemistry. This method is very simple and can synthesize the ceramic materials just by storing the mixture of raw materials added a small amount of water in a reactor at low temperature below 373 K. For example, Nano-size YVO4 (under 100 nm in diameter) was obtained using the SHR method.

DOI： 10.4028/www.scientific.net/KEM.690.268

Electrochemical Properties of LiFePO4 Cathode Materials Coated with Newly Developed Carbon Black Reviewed

Dai Okada, Takuma Sugiki, Kazuyoshi Uematsu, Atsushi Itadani, Kenji Toda, Mineo Sato, Togo Yamaguchi, Nozomi Arimitsu, Shogo Nishikawa

ELECTROCHEMISTRY 83 ( 10 ) 858 - 860 2015.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ELECTROCHEMICAL SOC JAPAN

A new type of carbon black CB1 was developed, by Asahi Carbon Co., Ltd., for usage of a lithium-ion battery (LIB). Compared with commercially available acetylene black, CB1 in which the network structure of carbon is developed has a relatively larger specific surface area. Therefore, CB1 dispersed in LiFePO4 precursors by planetary ball milling inhibited LiFePO4 primary particles' growth during calcination process. Charge/discharge performance was improved by coexistence of CB1 with polystyrene (PS) carbon layers deposited on LiFePO4 particle surfaces, compared to the performance for the LiFePO4 sample covered with carbon layers derived from only PS. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.83.858

Improvement of High Rate Performances for Ti-Doped Li3V2(PO4)(3) Cathode Materials Reviewed

Dai Okada, Fumiya Nakano, Kazuyoshi Uematsu, Hirokazu Okawa, Atsushi Itadani, Kenji Toda, Mineo Sato

ELECTROCHEMISTRY 83 ( 10 ) 828 - 830 2015.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ELECTROCHEMICAL SOC JAPAN

Ti-doped lithium vanadium(III) phosphate cathode materials, Li3-2x(V1-xTix)(2)(PO4)(3), were prepared by a solid state reaction. The Ti-doped samples exhibited that the gamma-phase is stabilized at room temperature by substituting Ti for V sites at more than x = 0.10. The discharge capacity of the doped samples at a 60C rate was found to be much higher than that for the non doped sample. This improved performance found for the doped cathodes was attributed to the increase in ionic conductivity given by the transition of alpha- to gamma-phase via Ti substitution. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.83.828

Novel green-emitting Ho3+-doped scandate phosphors Reviewed

Kazuma Sugimoto, Sun Woog Kim, Kazuyoshi Uematsu, Tadashi Ishigaki, Kenji Toda, Mineo Sato

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 123 ( 1441 ) 880 - 883 2015.9

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Blue-light excitable, green-light emitting Ba-3(Sc1-xHox)(4)O-9 phosphors were successfully synthesized in the single-phase form by a melt synthesis method for the first time. These phosphors show sharp green light emission under blue light (455 nm) excitation. The principal green light emission peak observed at 555 nm corresponds to the transition from F-5(4) and S-5(2) to the I-5(8) energy level of Ho3+. (C) 2015 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.123.880

Synthesis of YVO4 Nano Particles by Novel Room Temperature Synthesis Method Reviewed

Tatsuro Kaneko, Sun Woog Kim, Ayano Toda, Kazuyoshi Uematsu, Tadashi Ishigaki, Kenji Toda, Mineo Sato, Junko Koide, Masako Toda, Yoshiaki Kudo, Takaki Masaki, Dea Ho Yoon

SCIENCE OF ADVANCED MATERIALS 7 ( 8 ) 1502 - 1505 2015.8

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER SCIENTIFIC PUBLISHERS

Yttrium orthovanadate, YVO4 was prepared using a novel water assisted room temperature solid state reaction method, consisting of simply mixing of Y2O3 and V2O5 at room temperature with the addition of a small amount of water. Nano-scale spherical particles of YVO4 approximately 10-100 nm in diameter were obtained.

DOI： 10.1166/sam.2015.2364

Synthesis and Luminescent Properties of Novel Ca3Y3Ge2BO13:Ln(3+) (Ln(3+) = Tb3+ and Eu3+) phosphors Reviewed

Takuya Hasegawa, Natsuki Sato, Sun Woog Kim, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 123 ( 1438 ) 507 - 511 2015.6

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Novel Ln(3+)-doped (Ln(3+) = Tb3+ and Eu3+) and Eu3+, Bi3+ co-doped Ca3Y3Ge2BO13 phosphors were synthesized by a conventional solid-state reaction method. Tb3+- and Eu3+-doped phosphors showed strong narrow green and red emission due to 4f intra-shell transitions of the Tb3+ or Eu3+ ions under the excitation at 254 nm. Bi3+ co-doped Ca3Y3Ge2BO13:Eu3+ phosphor has a new broad strong excitation band appeared at around 302 nm due to S-1(0)-> P-3(1) transition of Bi3+, and presents red emission owing to 4f-4f transition of Eu3+ under excitation at 302 nm. (C)2015 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.123.507

Viscosity analysis of alkali metal carbonate molten salts at high temperature Reviewed

Sun Woog Kim, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 123 ( 1437 ) 355 - 358 2015.5

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

The viscosities of unary, binary, and ternary eutectic alkali metal carbonate molten salts were measured for the first time by a rotation method using a high-temperature rheometer system and the reliability of the viscosity values was evaluated. The viscosity values obtained in this study are similar to that reported by Sato's research group, which is considered to have the highest reliability among the studies reported till date. The standard errors in the viscosity values at each temperature are less than +/- 5%. (C) 2015 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.123.355

Luminescence and Morphology Control of Phosphor Materials Synthesized by Melt Synthesis Method Reviewed

K. Toda, T. Ishigaki, S. Kamei, S. W. Kim, K. Uematsu, M. Sato, M. Yoshimura

Applied Mechanics and Materials 752-753 221 - 224 2015.4

Synthesis of new green-emitting KBa1-xScSi3O9:Eu-x(2+) phosphors for white LEDs Reviewed

Takeshi Abe, Sun Woog Kim, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

OPTICAL MATERIALS 38 57 - 60 2014.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

New green-emitting KBa1-xScSi3O9:Eu-x(2+) phosphors for white LEDs were synthesized by a conventional solid-state reaction method. The obtained KBa1_xScSi3O9:Eu-x(2+) phosphors show the strong broad optical absorption band from UV to blue light region and exhibit broad green emission with a peak at 521 nm under excitation at 405 nm due to the allowed 4f(6)5d(1)-4f(7) transition of Eu2+. Optimization of Eu2+ concentration resulted in the highest green emission peak intensity was obtained at the composition of KBa0.94ScSi3O9:Eu-0.06(2+), and the relative emission intensity of this phosphor was 32% of that of a commercial YAG:Ce3+ phosphor. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optmat.2014.10.003

Synthesis and Photoluminescence Properties of HEu1-xGdx(MoO4)(2) Nanophosphor Invited Reviewed

Mizuki Watanabe, Kazuyoshi Uematsu, Sun Woog Kim, Kenji Toda, Mineo Sato

IEICE TRANSACTIONS ON ELECTRONICS E97C ( 11 ) 1063 - 1067 2014.11

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

New HEu1-xGdx(MoO4)(2) nanophosphors were synthesized by a simple one-step ion-exchange method. These nanophosphors have rod-like particle morphology with 0.5-15 mu m in length and outer diameters in the range of 50-500 nm. By optimization of the composition, the highest emission intensity was obtained for the samples with x = 0.50 for both KEu1-xGdx(MoO4)(2) and HEu1-xGdx(MoO4)(2).

DOI： 10.1587/transele.E97.C.1063

Site engineering concept of Ce3+-activated novel orange-red emission oxide phosphors Reviewed

Yukari Kawano, Sun Woog Kim, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Hiromitsu Takaba, Mineo Sato

OPTICAL MATERIALS EXPRESS 4 ( 9 ) 1770 - 1774 2014.9

Language：English Publishing type：Research paper (scientific journal) Publisher：OPTICAL SOC AMER

Novel Sr-6(Y1-xCex)(2)Al4O15 (0.005 <= x <= 0.20) phosphors were synthesized in a single phase form by a conventional solid-state reaction method. These phosphors can be achieved the emission color tunable from blue to orange-red by controlling the Ce3+ doping site in the Sr6Y2Al4O15 lattice and exhibit orange-red emission centered on 600 nm by blue light irradiation as the Ce3+ concentration was increased. To the best of our knowledge, this is the first report of Ce3+ doping oxide phosphor exhibiting orange-red emission centered on 600 nm under blue light excitation. (C) 2014 Optical Society of America

DOI： 10.1364/OME.4.001770

Influence of amorphous and crystalline type precursor intermediates on the morphology and luminescence properties of green emitting beta-Ca2SiO4:Eu2+ phosphor synthesized using a liquid phase precursor method Reviewed

Deok Su Jo, Jihae Kim, Karupannan Senthil, Hoo-Jeong Lee, Ho Kyoon Chung, Masato Kakihana, Toda Kenji, Takaki Masaki, Dae Ho Yoon

JOURNAL OF ALLOYS AND COMPOUNDS 608 311 - 317 2014.9

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Influence of precursor intermediates (PI) on the synthesis of high efficient green emitting beta-Ca2SiO4:Eu2+ (beta-C2S:Eu) phosphors were demonstrated by a novel liquid-phase-precursor (LPP) method utilizing (a) CaCl2-EuCl3, (b) Ca(NO3)(2)-EuCl3, (c) CaCl2-Eu(NO3)(3), and (d) Ca(NO3)(2)-Eu(NO3)(3) combinations as precursors. The crystallinity and morphology of the PI analyzed using X-ray diffraction and high-resolution transmission electron microscopy measurements showed both the amorphous and crystalline type precursor intermediates (API and CPI) depending upon the metal-source materials. The final morphology and luminescence properties of beta-C2S:Eu phosphors were found to be strongly influenced by the crystallinity (amorphous and crystalline) and morphology of the PIs. The APIs have led to regular-shaped homogeneous phosphor particles with higher luminescence when compared with the CPIs. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2014.04.133

Liquid Phase Precursor driven approach for the synthesis of Ca-Sr-Ba orthosilicate phosphors for white LED applications Reviewed

Neetu Tyagi, Deok Su Jo, Takeshi Abe, Kenji Toda, Takaki Masaki, Dae Ho Yoon

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 122 ( 1429 ) 806 - 809 2014.9

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Compositions of (CaSrBa) orthosilicate phosphors were prepared by Liquid Phase Precursor method. The structural phase determinations were done systematically by powder X ray diffraction and Transmission electron microscopy. The PL emission was observed under 450 and 375 nm excitation and green-red and pure green emission was observed for the 4f(6)5d -> 4f(7) transition of Eu2+ ion. The luminescence nature of the samples is determined to vary with crystal field effect on the Eu2+ ion and has been studied with the change in the binary Ca-Sr, Ba-Sr and ternary Ca-Sr-Ba compositions. (C) 2014 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.122.806

Novel Deep Red Emitting Phosphors Ca14Zn6M10:Mn4+ (M = Al3+ and Ga3+) Reviewed

Kohei Seki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

CHEMISTRY LETTERS 43 ( 8 ) 1213 - 1215 2014.8

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

This study investigated the luminescence properties of novel deep red phosphors Ca14Zn6M10O35:Mn4+ (M = Al3+ and Ga3+). These phosphors efficiently excited using a blue LED light. It exhibited a deep red emission around 713 nm. The luminescence intensities of CZA:Mn-0.03 and CZG:Mn-0.03 excited at 450 nm were, respectively, about 2.2 and 2.7 times higher than that of YAG:Ce3+ (P46). These phosphors also show little temperature quenching, but more than that shown by YAG:Ce3+ at 423 K. These results show that the deep red phosphor Ca14Zn6M10O35:Mn4+ (M = Al3+ and Ga3+) is a beneficial phosphor for use in indoor plant cultivation.

DOI： 10.1246/cl.140227

Synthesis of Eu2+-activated Rb-Ba-Sc-Si-O glass phosphors using melt synthesis technique Reviewed

Sun Woog Kim, Takuya Hasegawa, Michiyo Inoue, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 122 ( 1426 ) 452 - 463 2014.6

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Eu2+-activated Rb-Ba-Sc-Si-O glass phosphor was synthesized by a melt synthesis technique using arc-imaging furnace and their photoluminescence properties were characterized. In addition, the obtained glass phosphors annealed in a flow of 5%H-2-95% Ar gas to enhance the luminescent efficiency. The emission spectra of the Eu2+-activated glass phosphors presents yellow emission band centered at 537nm due to the 4f(6)5d(1) -> 4f(7) transition of Eu2+, and the emission intensity was effectively enhanced by the annealing treatment. (C) 2014 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.122.452

Novel Reddish Yellow-emitting Ce3+-Doped Ba3Sc4O9 Phosphors for Blue-light-based White LEDs Reviewed

Takuya Hasegawa, Sun Woog Kim, Tadashi Ishigaki, Kazuyoshi Uematsu, Hiromitsu Takaba, Kenji Toda, Mineo Sato

CHEMISTRY LETTERS 43 ( 6 ) 828 - 830 2014.6

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

Novel reddish yellow-emitting Ba-3(Sc1-xCex)(4)O-9 (0 <= x <= 0.01) phosphors were synthesized in a single-phase form by a conventional solid-state reaction method. These phosphors exhibited excellent optical absorption in the blue-light region and showed reddish yellow emission with a peak at 583 urn due to the 5d -> 4f transition of Ce3+ under excitation at 437 nm. By optimizing the Ce3+ concentration, the maximum emission intensity was obtained for Ba-3(Sc0.999Ce0.001)(4)O-9.

DOI： 10.1246/cl.140070

Synthesis of FeF3 fluoride electrode material using polytetrafluoroethylene Reviewed

Hirotaka Torii, Kazuyoshi Uematsu, Tadashi Ishigaki, Kenji Toda, Mineo Sato

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 122 ( 1426 ) 473 - 476 2014.6

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

A fluoride electrode material for lithium-ion batteries, FeF3, was synthesized by a novel solid-state reaction method using polytetrafluoroethylene (PTFE) as a fluoride source instead of HF. FeF3 was obtained as the main phase according to the XRD patterns of the samples prepared in the present study. Furthermore, the synthesized FeF3 particles were nanosize. The initial discharge and charge capacities of the FeF3 sample were 387 and 293mAh/g, respectively, in the 4.5-1.0V region. (C) 2014 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.122.473

Synthesis of blue-emitting (K <inf>1-x</inf>Na <inf>x</inf>)Mg <inf>4</inf>(PO <inf>4</inf>)<inf>3</inf>:Eu <sup>2+</sup> phosphors Reviewed

Sun Woog Kim, Takuya Hasegawa, Tadashi Ishigaki, Kazuyoshi Uematsu, Mineo Sato, Kenji Toda

Journal of Information Display 15 ( 2 ) 53 - 57 2014.4

Language：English Publishing type：Research paper (scientific journal)

Blue-emitting (K 1-xNa x)Mg 4(PO 4)3:Eu 2+ phosphors were synthesized through a conventional solid-state reaction method, and their photoluminescence properties were characterized. These phosphors exhibited the typical emission band assigned to the transition from 4f65d1 to 4f7 of Eu2+, and the emission intensity was effectively enhanced by Na +-doping into the host lattice. The highest blue emission peak intensity was obtained for (K 0.65Na 0.35)Mg 4(PO 4)3:1 mol%Eu2+, where the relative emission peak intensity was 33% of that for the commercial blue-emitting BaMgAl 10O 17:10 mol%Eu 2+ phosphor. In addition, these phosphors have excellent thermal stability in the temperature quenching effect. © 2014 © 2014 The Korean Information Display Society.

DOI： 10.1080/15980316.2014.907213

SrxAl2O4:Eu0.0152+Dy0.033+ (x=1.1-1.7) green emitting phosphors with efficient emissive properties Reviewed

Neetu Tyagi, Deok Su Jo, Takeshi Abe, Kenji Toda, Sang-Jun Lee, Sung Gook Oh, Takaki Masaki, Dae Ho Yoon

JOURNAL OF LUMINESCENCE 147 245 - 249 2014.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Monophasic SrAl2O4:Eu2+ Dy3+ with varying Sr2+ concentration was synthesized in monoclinic symmetry by the Liquid Phase Precursor method. The composition Sr1.7Al2O4:Eu0.0152+Dy0.033+ showed the 200% emission compared with commercial Sr0.97Al2O4:Eu-0.01(2+) Dy-0.02(3+). Time decay measurements of the doped samples were conducted for the green emission at 525 nm. All the prepared samples exhibit rapid decay and ensued phosphorescence with the longer decay times which are comparable to the commercial sample. Quantum yield product measurements results suggested that the synthesized phosphors show enhanced emissive properties over the commercial phosphor. The composition Sr1.7Al2O4:Eu0.0152+Dy0.033+ had a photoluminescence quantum yield of 31.63%, nearly 12.7% more than the commercial sample. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jlumin.2013.11.018

Accelerating the emission properties beyond the skidding effect of varying Sr, Eu and Dy concentration in SrAl2O4 : Eu Dy phosphors Reviewed

N. Tyagi, D. S. Jo, K. Toda, T. Masaki, D. H. Yoon

JOURNAL OF CERAMIC PROCESSING RESEARCH 15 ( 4 ) 251 - 255 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：KOREAN ASSOC CRYSTAL GROWTH, INC

Eu and Dy-doped strontium aluminate is a long-lasting phosphor for practical applications in displays and emergency signage. SrAl2O4 synthesized samples have been systematically investigated by PXRD, SEM and photoluminescence. The optimization of the properties has been determined in terms of varying concentrations of Sr2+ (alkali metal ion concentration) and the dopant concentrations of Eu2+ and Dy3+. A new method of synthesis requiring hydrate solutions of the metal ions and cellulose precursor called Liquid Phase Precursor method (LPP) has been adapted. The emission intensity was observed to be higher for the prepared samples compared to a commercial product prepared with a solid state reaction method.

Synthesis and the luminescent properties of silicate NaAlSiO4:Eu2+ phosphor using SiO powder as a silica source Reviewed

Takeshi Abe, Kenji Toda, Kazuyoshi Uhematsu, Mineo Sato, Tadashi Ishigaki, Kim Bong Sung, Deok Su Jo, Takaki Masaki, Dae Ho Yoon

ELECTROCERAMICS IN JAPAN XVI 582 214 - + 2014

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

A yellow-emitting NaAlSiO4:Eu2+ phosphor was synthesized using SiO powder as a reducing agent and a silica source material. The emission intensity of the NaAlSiO4:Eu2+ phosphor synthesized using SiO powder is higher than that of a sample produced using a conventional silicate phosphor synthesis reaction using SiO2 powder. The ratio of non-reduced Eu3+ ions in the NaAlSiO4:Eu2+ phosphor synthesized using SiO powder was decreased by the reduction effect of SiO powder.

DOI： 10.4028/www.scientific.net/KEM.582.214

Title Synthesis and photoluminescence properties of Mn2+ co-doped white emitting (Sr,Sn)ZnP2O7 phosphor Reviewed

Sun Woog Kim, Takuya Hasegawa, Hiroyuki Yumoto, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

JOURNAL OF CERAMIC PROCESSING RESEARCH 15 ( 3 ) 177 - 180 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：KOREAN ASSOC CRYSTAL GROWTH, INC

Rare earth-free white emitting (Sr,Sn)(Zn,Mn)P2O7 phosphors were synthesized in a single phase form by a conventional solid-state reaction method and photoluminescent properties were characterized. These phosphors showed three broad band in emission spectra at 340, 440, and 690 nm, and the ratio of emission intensity between blue-green light and red light changes with Mn2+ content increasing because of energy transfer from Sn2+ to Mn2+. The emission color of the phosphors varied from blue-white to orange-white with the increase in the Mn2+ content and the emission color of the (Sr0.90Sn0.10)(Zn0.97Mn0.03)P2O7 phosphor was very close to white light.

A novel bluish green-emitting RbBaScSi3O9 : Eu2+ phosphor for white LEDs Reviewed

Takeshi Abe, Sun Woog Kim, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

JOURNAL OF CERAMIC PROCESSING RESEARCH 15 ( 3 ) 181 - 184 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：KOREAN ASSOC CRYSTAL GROWTH, INC

A novel bluish green-emitting silicate phosphor, RbBaScSi3O9 : Eu2+, was synthesized by a conventional solid state reaction method. The RbBaScSi3O9 : Eu2+ phosphor can be excited by a near-UV and blue light irradiation and presents a bluish green band centered at 500 nm due to the allowed transition from 4f(6)5d(1) to 4f(7) of Eu2+. The maximum emission peak intensity was obtained at the composition of RbBaScSi3O9 : 10 mol% Eu2+, and the emission intensity was 13% compared with that of the commercial YAG phosphor.

Synthesis and photoluminescence properties of HEu(MoO4)(2) nanophosphor Reviewed

Mizuki Watanabe, Kazuyoshi Uematsu, Sun Woog Kim, Kenji Toda, Mineo Sato

JOURNAL OF CERAMIC PROCESSING RESEARCH 15 ( 3 ) 173 - 176 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：KOREAN ASSOC CRYSTAL GROWTH, INC

The HEu(MoO4)(2) nanophosphor was synthesized for the first time by the H+-exchange of KEu(MoO4)(2). The nanophosphor obtained in the present study maintain the triclinic KEu(MoO4)(2) type structure in a single phase form with high crystallinity. The HEu(MoO4)(2) phosphor has rod-like particle morphology (length 0.5-20 mu m, diameter 50-400 nm). Both HEu(MoO4)(2) powder and solution shows red emission due to the 4f-4f transition of Eu3+.

Synthesis and the luminescent properties of NaAlSiO4:Eu2+ phosphor using SiO powder as a silica source Reviewed

Takeshi Abe, Sun Woog Kim, Tadashi Ishigaki, Kazuyoshi Uematsu, Mineo Sato, Takaki Masaki, Dae Ho Yoon, Kenji Toda

Journal of Information Display 15 ( 1 ) 31 - 35 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：E-flow Taylor and Francis

A yellow-emitting silicate phosphor, NaAlSiO4:Eu2+, was synthesized through a new reducing technique, using SiO powder as a silica source, during the preparation process. The addition of SiO powder as a silica source significantly enhanced the Eu2+ content, which led to an increase in the photoluminescence emission intensity of the NaAlSiO4:Eu2+ phosphor. The optimization of the composition resulted in obtaining the maximum emission intensity for NaAlSiO4:7 mol% Eu2+. © 2014 The Korean Information Display Society.

DOI： 10.1080/15980316.2014.886628

Synthesis of down-converting red emission Ca14Zn6Al10-xMnxO35 phosphors for use in solar cells Reviewed

Mangyu Hur, Takaki Masaki, Kenji Toda, Dae Ho Yoon

JOURNAL OF CERAMIC PROCESSING RESEARCH 15 ( 3 ) 197 - 199 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：KOREAN ASSOC CRYSTAL GROWTH, INC

Ca14Zn6Al10-xMnxO35 (x = 1, 3, 5 mol%, CZAMO) phosphor materials were synthesized using the liquid phase precursor (LPP) method. Nanostructrued cellulose was impregnated with metal-hydrate solution and then calcined to vaporize the cellulose. The impregnated cellulose was fired at 800 to 1200 degrees C to give the CZAMO phosphors. The particle size and crystal structure of the phosphors were analyzed by FE-SEM and XRD. Nano-sized particles with a dominant Ca14Zn6Al10O35 structure (100 nm) were obtained by firing at 800 degrees C for 1 h. The red emission wavelength of the phosphors ranged from 650 to 750 nm, peaking at 713 nm.

Long phosphorescent Ca2SnO4 with minuscule rare earth dopant concentration Reviewed

Tadashi Ishigaki, Akiko Torisaka, Kentarou Nomizu, Puttaswamy Madhusudan, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

Dalton Transactions 42 ( 14 ) 4781 - 4785 2013.4

Language：English Publishing type：Research paper (scientific journal)

Rare-earth doped Ca2SnO4 phosphors were synthesized using a conventional solid state reaction method. The red phosphorescence of Eu3+ was observed in this system with persistence time. In the as-prepared samples, the doped rare earth ions occupied both Ca and Sn sites in the host lattice. The longest phosphorescent persistence property can be achieved for the Ca2SnO4 phosphors with a 0.1% Eu dopant. Depending on the doped rare earth ions, afterglow emissions of various colors were observed. © 2013 The Royal Society of Chemistry.

DOI： 10.1039/c3dt33079f

Research on new precursor for nanosheets phosphors Reviewed

K. Tanima, M. Watanabe, Y. Imanari, S. Kamei, K. Uematsu, T. Shigaki, K. Toda, M. Sato, T. Masaki, D. H. Yoon

Journal of Ceramic Processing Research 14 ( 1 ) s71 - s73 2013.3

Luminescent properties of Eu-activated Mg-Y-Si-O-N glass and crystalline phosphors Reviewed

S. Sato, S. Kamei, K. Uematsu, T. Ishigaki, K. Toda, M. Sato, H. Sasaoka, M. Ooka, K. Nishimura

Journal of Ceramic Processing Research 14 ( 1 ) s77 - s79 2013.3

Synthesis of broadband emission phosphor Ca2KMg2(V1xPx)(3)O-12 for white light emitting diodes Reviewed

M. Maeda, K. Uematsu, S. Kamei, T. Ishigaki, K. Toda, M. Sato

JOURNAL OF CERAMIC PROCESSING RESEARCH 14 ( 1 ) S60 - S63 2013.3

Language：English Publishing type：Research paper (scientific journal) Publisher：KOREAN ASSOC CRYSTAL GROWTH, INC

We report the increased emission intensity of Ca2KMg2V3O12 by partially substituting the V5+ ion for the P5+ ion. The emission intensity of Ca2KMg2(V0.95P0.05)(3)O-12 was approximately 1.3 times greater than that of Ca2KMg2V3O12. The obtained phosphors were excited and emitted at 360 nm and 520 nm, respectively, and the emission obtained as a greenish white emission. The color coordinates of Ca2KMg2(V0.95P0.05)(3)O-12 were x = 0.377 and y = 0.463.

Synthesis of Zn2SiO4:Mn2+ using SiOx as an oxidation inhibitor Reviewed

T. Sakamoto, S. Kamei, K. Uematsu, T. Ishigaki, K. Toda, M. Sato

Journal of Ceramic Processing Research 14 ( 1 ) s64 - s66 2013.3

Enhancement of photoluminescence properties of SrAl2Si2O8:Eu2+ by a large amount of SiO2 addition Reviewed

B. S. Kim, Y. H. Song, D. S. Jo, T. Abe, K. Senthil, T. Masaki, K. Toda, D. H. Yoon

JOURNAL OF CERAMIC PROCESSING RESEARCH 14 ( 1 ) S12 - S14 2013.3

Synthesis and luminescence properties of rare earth doped Na3AlP3O9N oxynitridophosphate phosphor Reviewed

S. Sato, S. Kamei, K. Uematsu, T. Ishigaki, K. Toda, M. Sato, H. Sasaoka, M. Ooka, K. Nishimura

Journal of Ceramic Processing Research 14 ( 1 ) s74 - s76 2013.3

Enhancement of the luminescence efficiency of Li2TiO3:Mn4+ red emitting phosphor for white LEDs Reviewed

K. Seki, S. Kamei, K. Uematsu, T. Ishigaki, K. Toda, M. Sato

Journal of Ceramic Processing Research 14 ( 1 ) s67 - s70 2013.3

Efficient red emission of blue-light excitable new structure type NaMgPO<inf>4</inf>:Eu<sup>2+</sup> phosphor Reviewed

Sun Woog Kim, Takuya Hasegawa, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

ECS Solid State Letters 2 ( 12 ) R49 - R51 2013

Language：English Publishing type：Research paper (scientific journal)

A novel red-emitting olivine-type NaMgPO4:Eu2+ phosphor was synthesized for the first time by the melt synthesis technique using arc-imaging furnace. The NaMgPO4:Eu2+ phosphor can be efficiently excited by blue light irradiation and presents red emission band centered at 628 nm due to the 4f65d1 → 4f7 transition of Eu2+. The highest emission peak intensity was obtained for NaMgPO4:2.5mol%Eu2+, and the internal quantum efficiency of this phosphor at the excitation wavelength of 450 nm was 81%. Furthermore, these phosphors show an excellent thermal stability on the temperature quenching effect. © 2013 The Electrochemical Society.

DOI： 10.1149/2.004312ssl

Synthesis and Photoluminescence Studies of Eu3+ Activated Borosilicate Phosphor (Gd1-xEux)(3)BSi2O10 for White Light Emitting Diodes Reviewed

Tadashi Ishigaki, Puttaswamy Madhusudan, Michiyo Inoue, Shinnosuke Kamei, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY 2 ( 2 ) R3018 - R3020 2013

Language：English Publishing type：Research paper (scientific journal) Publisher：ELECTROCHEMICAL SOC INC

Certain silicate materials with different crystal structures show excellent luminescence properties. Furthermore, these silicate compounds have high chemical and thermal stability and considered as an excellent phosphor host materials. In this study, we report (Gd1-xEux)(3)BSi2O10 as a novel ultraviolet (UV) excited white phosphors prepared under solid state reaction and their luminescence properties at 393 nm excitation were investigated in detail. The as prepared (Gd1-xEux)(3)BSi2O10 phosphors showed red emission with UV (around 580-630 nm) and near-UV light (around 250-410 nm). The chromaticity coordinates (0.60, 0.34) of the prepared borosilicate phosphor were very close to the NTSC standard value (0.67, 0.33) and its emission intensity was almost similar to commercial red phosphor Y2O2S:0.05Eu(3+). Further, as prepared (Gd1-xEux)(3)BSi2O10 material is considered to be an efficient red-emitting phosphor for UV based light emitting diodes (LED). (C) 2012 The Electrochemical Society.

DOI： 10.1149/2.007302jss

Hydrothermal synthesis of meso/macroporous BiVO4 hierarchical particles and their photocatalytic degradation properties under visible light irradiation Reviewed

Puttaswamy Madhusudan, Malahalli Vijaya Kumar, Tadashi Ishigaki, Kenji Toda, Kazuyoshi Uematsu, Mineo Sato

Environmental Science and Pollution Research 20 ( 9 ) 6638 - 6645 2013

Language：English Publishing type：Research paper (scientific journal)

An ordered hierarchical meso/macroporous monoclinic bismuth vanadate (BiVO4) particle was fabricated for the first time by a simple two-step melamine template hydrothermal method followed by calcination. The physiochemical parameters of as-prepared porous materials were characterized by means of X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Raman, Barrett-Emmett-Teller, and UV-vis techniques. The nitrogen adsorption-desorption measurement and pore size distribution curve suggest that meso/macropores exist in these hierarchical microarchitectures. Further, it is found that melamine plays a significant role in the formation of porous BiVO4 particles, and when a known amount of melamine was added, the surface area and pore size of such porous BiVO4 particles were increased. The photocatalytic activities of the as-prepared hierarchical BiVO4 samples were measured for the photodegradation of Congo red aqueous dye solution under visible light irradiation. Surprisingly, the porous BiVO4 particles showed outstanding photocatalytic activities than polycrystalline BiVO4 sample. The possible enhancement of such catalytic performance has also been further discussed. © 2013 Springer-Verlag Berlin Heidelberg.

DOI： 10.1007/s11356-013-1694-x

Enhancement of photoluminescence properties of CaAl2Si2O8:Eu2+ by SiO2 addition Reviewed

B. S. Kim, Y. H. Song, D. S. Jo, T. Abe, K. Senthil, T. Masaki, K. Toda, D. H. Yoon

MATERIALS RESEARCH BULLETIN 47 ( 10 ) 3015 - 3019 2012.10

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

SiO2 added phosphors, CaAl2Si2O8:Eu2+ + xSiO(2) (x = 0, 1, 2, 3, 4, 5, 6 and 13 mol) were synthesized by a novel liquid phase precursor (LPP) method. The photoluminescence properties of phosphor added by 5 mol of SiO2 showed 110% enhancement in the emission intensity compared to the CaAl2Si2O8:Eu2+ phosphor. A broad emission and excitation wavelength was observed approximately from 400 nm to 600 nm centered at 430 nm and from 280 nm to 400 nm centered at 365 nm, respectively. Photoluminescence intensity of the phosphors increased continuously by SiO2 addition up to x = 5 mol and then it decreased with further addition of SiO2. The observed photoluminescence properties of the phosphors were discussed related to their crystalline structure and morphology. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.materresbull.2012.04.109

Redetermination of the low-temperature polymorph of Li 2MnSiO4 from single-crystal X-ray data Reviewed

Mineo Sato, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Hirokazu Okawa

Acta Crystallographica Section E: Structure Reports Online 68 ( 9 ) i68 - i69 2012.9

Language：English Publishing type：Research paper (scientific journal)

Crystals of dilithium manganese(II) silicate were grown under high-temperature hydro-thermal conditions in the system LiOH - MnO2 - SiO2. The title compound crystallizes in the ΒII-Li 3PO4 structure type. The coordination polyhedra of all cations are slightly distorted tetra-hedra (m symmetry for MnO4 and SiO4), which are linked by corner-sharing to each other. The vertices of the tetra-hedra point to the same direction perpendicular to the distorted hexa-gonal close-packed (hcp) array of O atoms within which half of the tetra-hedral voids are occupied by cations. In comparison with the previous refinement from powder X-ray data [Dominko et al. (2006). Electrochem. Commun. 8, 217-222], the present reinvestigation from single-crystal X-ray data allows a more precise determination of the distribution of the Li+ and Mn2+ cations, giving a perfectly site-ordered structure model for both Li+ and Mn2+.

DOI： 10.1107/S1600536812035040

Photoluminescence properties of Ba3Si6O12N2:Eu2+ oxynitride phosphor synthesized by liquid phase precursor method Reviewed

Y. H. Song, M. O. Kim, M. K. Jung, K. Senthil, T. Masaki, K. Toda, D. H. Yoon

MATERIALS LETTERS 77 121 - 124 2012.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Ba3Si6O12N2 green-emitting phosphors were synthesized using oxide precursor by liquid phase precursor (LPP) method under a flowing NH3 gas. X-ray diffraction patterns showed that the prepared phosphor indicated a Ba3Si6O12N2 pure single phase. The emission spectra of synthesized phosphors under excited from UV to blue light showed a typically broad green emission wavelength which is assigned to 4f(6)5d -> 4f(7) electronic transition of Eu2+ ion. Compared with emission intensity of prepared sample, the emission intensity of Ba3- Si6O12N2 green-emitting phosphors using LPP method is more than 2.5 times than that of Ba3Si6O12N2 green-emitting one by a solid state reaction method. The synthesis of phosphor using the LPP method is expected as alternative synthesis method. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2012.02.131

Synthesis of high efficient Ca2SiO4:Eu2+ green emitting phosphor by a liquid phase precursor method Reviewed

Y. Y. Luo, D. S. Jo, K. Senthil, S. Tezuka, M. Kakihana, K. Toda, T. Masaki, D. H. Yoon

JOURNAL OF SOLID STATE CHEMISTRY 189 68 - 74 2012.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE

Green emitting Eu2+-doped Ca2SiO4 phosphors were synthesized by three different methods (a conventional solid state reaction (SSR) method, a novel liquid phase precursor approach using SiO2 sol (LPP-SiO2(sol)) and water-soluble silicon compound (LPP-WSS)). The obtained phosphors exhibited a broad excitation spectrum ranging from 225 to 450 nm and a strong green emission peak at 502 nm due to the 4f(6)5d(1)-> 4f(7)(S-8(7/2)) transition of Eu2+. The highest luminescent intensity was obtained for the samples fired at 1100 degrees C. The dependence of luminescence properties on Eu2+ concentration for the phosphors synthesized using LPP-WSS method was also examined from 0.1 to 5.0 mol% and the maximum emission intensity was observed at 3.0 mol% Eu2+. A detailed analysis using various characterizations revealed that phosphors produced by the LPP-WSS process exhibited more homogenous phase distribution and higher luminescence intensity than those from the other two processes, which suggested the potential application of Ca2SiO4:Eu2+ in white light-emitting diodes and fluorescence lamps. (C) 2011 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jssc.2011.11.046

Synthesis and photoluminescence properties of new NaAlSiO4:Eu2+ phosphors for near-UV white LED applications Reviewed

Deok Su Jo, YuanYuan Luo, Karuppanan Senthil, Kenji Toda, Bong Sung Kim, Takaki Masaki, Dae Ho Yoon

OPTICAL MATERIALS 34 ( 4 ) 696 - 699 2012.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

A new NaAlSiO4:0.1Eu(2+) phosphors were synthesized at different temperatures using a liquid phase precursor (LPP) technique. The XRD patterns indicate the presence of hexagonal nepheline phase for all the samples. The synthesized phosphors can be excited efficiently in the broad near-UV region. The PL emission spectra showed a broad emission peak at around 551 nm corresponding to 5d -> 41 transition of Eu2+ ions. The synthesized phosphors showed better thermal stability when compared with the standard YAG:Ce3+ phosphor. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optmat.2011.10.004

New processing of LED phosphors Reviewed

Kenji Toda

Transactions on Electrical and Electronic Materials 13 ( 5 ) 225 - 228 2012

Language：English Publishing type：Research paper (scientific journal) Publisher：Korean Institute of Electrical and Electronic Material Engineers

In order to synthesize LED phosphor materials, we have applied three novel synthesis techniques, "melt synthesis", "fluidized bed synthesis" and "vapor-solid hybrid synthesis", in contrast with the conventional solid state reaction technique. These synthesis techniques are also a general and powerful tool for rapid screening and improvements of new phosphor materials. © 2012 KIEEME.

DOI： 10.4313/TEEM.2012.13.5.225

Synthesis and Photoluminescence Properties of Green-Emitting Ba3Si6O12N2 Oxynitride Phosphor Using Boron-Coated Eu2O3 for White LED Applications Reviewed

Y. H. Song, B. S. Kim, M. K. Jung, K. Senthil, T. Masaki, K. Toda, D. H. Yoon

JOURNAL OF THE ELECTROCHEMICAL SOCIETY 159 ( 5 ) J148 - J152 2012

Language：English Publishing type：Research paper (scientific journal) Publisher：ELECTROCHEMICAL SOC INC

Highly efficient Ba3Si6O12N2 green-emitting phosphors using boron-coated Eu2O3 were synthesized by a gas reduction nitridation method under flowing NH3 gas. X-ray diffraction patterns showed that the synthesized phosphor was a pure phase of Ba3Si6O12N2. The Ba3Si6O12N2 green-emitting phosphors synthesized by modification of an alumina boat were crystallized much better as well as showed higher emission intensity. The emission spectra showed a typically broad green emission band attributed to the 4f(6)5d-->4f(7) electronic transition of Eu2+ ions under excitation at 405 nm. The green-emitting Ba3Si6O12N2 phosphors that were synthesized using boron-coated Eu2O3 by modification of an alumina boat could be applied to generate white light emitting diodes. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.047205jes] All rights reserved.

DOI： 10.1149/2.047205jes

Combinatorial synthesis of phosphors（共著） Reviewed

T. Ishigaki, K. Toda, M. Yoshimura, K. Uematsu, M. Sato

Science and Technology of Advanced Materials 12 054205 2011.11

A new raw material SiO for the synthesis of silicate phosphors Reviewed

K. Toda

Journal of Ceramic Processing Research 12 ( 3 ) s256 - s258 2011.11

Synthesis of CaMgGe2O6:Mn2+ phosphors for field emission lamps （共著） Reviewed

S. Sato, K. Uematsu, T. Ishigaki, K.Toda, M. Sato, H. Sasaoka, M. Ooka, K. Nishimura

Journal of Ceramic Processing Research 12 ( 3 ) s278 - s281 2011.11

Synthesis of Mn4+ doped red emitting phosphor for white LEDs（共著） Reviewed

K. Seki, K. Uematsu, T. Ishigaki, K. Toda, M. Sato

Journal of Ceramic Processing Research 12 ( 3 ) s286 - s288 2011.11

Synthesis of Ba2SiO4:Eu2+ by a gas-solid phase method （共著） Reviewed

T. Sakamoto, K. Uematsu, T. Ishigaki, K. Toda, M. Sato

Journal of Ceramic Processing Research 12 ( 3 ) s272 - s274 2011.11

New rare earth-free red emitting phosphor SiP2O7:Mn2+ and 4+ Under UV light excitation（共著） Reviewed

M. Maeda, K. Uematsu, T. Ishigaki, K. Toda, M. Sato

Journal of Ceramic Processing Research 12 ( 3 ) s263 - s266 2011.11

Crystal Growth of Silicate Phosphors from the Vapor Phase Invited Reviewed

Tadashi Ishigaki, Kenji Toda, Tatsuya Sakamoto, Kazuyoshi Uematsu, Mineo Satot

IEICE TRANSACTIONS ON ELECTRONICS E94C ( 11 ) 1745 - 1748 2011.11

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

Well-crystallized Ba2SiO4:Eu2+ powders were grown on a substrate by the vapor phase reaction between a mixed powder (barium carbonate and europium oxide) and SiO gas. The vaporization of SiO occurs at 1400-1600 degrees C from the SiO2 source (or SiO powder) in a reducing atmosphere. The formed SiO gas was transported by 95 vol% Ar - 5 vol% H-2 gas and reacted with the raw material powders. The emission intensity of the Ba2SiO4:Eu2+ phosphor synthesized by the new vapor phase technique is about 2.6 times higher than that of a conventional solid-state reaction sample.

DOI： 10.1587/transele.E94.C.1745

A new yellowish green NaAl(SiO4):Eu2+ phosphor for UV-LED using a liquid phase precursor process（共著） Reviewed

D. S. Jo, K. H. Choi, K. Toda, T. Masaki, D. H. Yoon

Jornal of Ceramic Processing Research 12 ( 1 ) s47 - s50 2011.3

Synthesis and properties of Na3YSi2O7:Eu3+ phosphor for fluorescent lamp Reviewed

T. Sakamoto, S. Kousaka, K. Uematsu, T. Ishigaki, K. Toda, M. Sato

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 9 8 ( 9 ) 2731 - 2734 2011

Language：English Publishing type：Research paper (international conference proceedings) Publisher：WILEY-V C H VERLAG GMBH

Eu3+ doped Na3YSi2O7 phosphors were prepared by a solid state reaction. It was found that the excitation spectra included two regions: i.e. the broad excitation band at 237 nm and narrow peaks at 395 nm and 463 nm. The peak located at 237 nm was assigned to the combination of the charge transfer transition of O-Eu, while the peaks at 395 nm and 463 nm were assigned to the f-f transitions of Eu3+. The emission spectrum was dominated by the red peak located at 612 nm due to the electric dipole transition of D-5(0)-F-7(2). The Eu3+ doped Na3YSi2O7 phosphor was suitable for use in fluorescent lamps and white LED applications. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

DOI： 10.1002/pssc.201084125

Synthesis of Eu2+-doped A-site and oxygen-deficient perovskite related host for photoluminescent materials Reviewed

Tadashi Ishigaki, Tomoki Hatsumori, Tatsuya Sakamoto, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 9 8 ( 9 ) 2728 - 2730 2011

Language：English Publishing type：Research paper (international conference proceedings) Publisher：WILEY-V C H VERLAG GMBH

Perovskite-related compounds have been investigated in many fields, because they have various unique properties due to their compositions and structures which are characterized by various combinations of the A and B cations. In addition, defect perovskite-type compounds have also been investigated in many areas, especially as ion conductors. In this study, we used the A-site and oxygen-deficient perovskite, Sr3Al2O6, as a photoluminescent host material. This means that the defect sites were able to substitute several ions. We investigated the A(3)Al(2)O(6):Eu2+ phosphor material (A = Mg, Ca, Sr, Ba) produced by a solid state reaction in several kinds of atmospheres. Based on our results, the phosphor showed wide excitation and emission bands of 300-400 nm and 450-600 nm, respectively. The emission color control depended on the A-site substitution ratio. It is a very useful phosphor for white LEDs. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

DOI： 10.1002/pssc.201084140

Development of gas-solid phase hybrid synthesis method of single crystal Ba2SiO4:Eu2+ Reviewed

Tatsuya Sakamoto, Kazuyoshi Uematsu, Tadashi Ishigaki, Kenji Toda, Mineo Sato

ELECTROCERAMICS IN JAPAN XIV 485 325 - + 2011

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

We succeeded in the single crystal growth of Ba2SiO4:Eu2+ by novel synthesis method which was gas (SiO) and solid (Ba - Sc - Al - Eu - 0) phase hybridized. The Ba2SiO4:Eu2+ single crystal was synthesized by interfacial crystal growth after the reaction of the SiO gas with the surface of Ba - Sc - Al - Eu - O substrate in the reductive atmosphere. The single crystals were plate-like crystals with about 500 mu m sizes and emitted green light around 500 nm under 300 - 450 nm excitation.

DOI： 10.4028/www.scientific.net/KEM.485.325

Synthesis of anataseTiO(2) having high specific surface area from a gel precursor Reviewed

Keiko Fukushi, Sae Nakajima, Kazuyoshi Uematsu, Tadashi Ishigaki, Kenji Toda, Mineo Sato

ELECTROCERAMICS IN JAPAN XIV 485 279 - + 2011

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

Anatase TiO2 having high temperature stability and specific surface area was synthesized using a gel precursor in very mild conditions. The precursor gel was obtained by dialysis treatment of Na16Ti10O28-HNO3 solution. The samples were characterized by X-ray diffraction analysis, transmission electronmicroscopy, Brunner-Emmett-Teller method for specific surface area measurements, and thermogravimetric analysis.

DOI： 10.4028/www.scientific.net/KEM.485.279

Microwave synthesis technique for long phosphorescence phosphor SrAl2O4:Eu2+, Dy3+ using carbon reduction Reviewed

Tadashi Ishigaki, Hitomi Mizushina, Kazuyoshi Uematsu, Nobuhiro Matsushita, Masahiro Yoshimura, Kenji Toda, Mineo Sato

MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS 173 ( 1-3 ) 109 - 112 2010.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

As described herein, we prepared SrAl2O4:Eu2+, Dy3+ phosphor using a domestic microwave oven operated at 2.45 GHz with 500 Win 30 min, processes with carbon reduction. Using carbon as the microwave absorber it generates thermal energy. Furthermore, heating with carbon can provide a reductive atmosphere. Prepared samples emitted phosphorescence emission for a long time. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.mseb.2009.11.004

Synthesis and luminescence property of new phosphate phosphor, RbPO3:Tb Reviewed

Ayano Toda, Kazuyoshi Uematsu, Tadashi Ishigaki, Kenji Toda, Mineo Sato

MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS 173 ( 1-3 ) 168 - 170 2010.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Luminescence property of a new phosphate phosphor, RbPO3:Tb, is reported in this paper. A single phase sample was obtained by thermal decomposition of a raw material mixture (RbH2PO4 and Tb4O7) at 973 K. The phosphor could be efficiently exited by the UV light, yielding an intense green emission around 550 nm. The intense green emission is originated from the f-f transition of Tb3+ ion. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.mseb.2009.12.025

Synthesis and characterization of low-dimensional structure Reviewed

M. Nishiya, K. Uematsu, T. Ishigaki, K. Toda, M. Sato

Key Engineering Materials 445 191 - 194 2010.6

Morphology control of phosphors synthesized by microwave heating method Reviewed

A. Toda, K. Uematsu, T. Ishigaki, K. Toda, M. Sato

Key Engineering Materials 445 233 - 236 2010.6

Low temperature synthesis method of La2O2S2 and evaluation of the photocatalytic activity Reviewed

M. Ohashi, T. Ishigaki, K. Uematsu, K. Toda, M. Sato

Key Engineering Materials 445 217 - 220 2010.6

Melt synthesis of Eu-doped oxide phosphors using arc-imaging furnace Reviewed

Tadashi Ishigaki, Masahiro Yoshimura, Nobuhiro Matsushita, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 30 ( 2 ) 165 - 169 2010.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

To synthesize various complex oxide materials and their solid solutions, we applied a novel "melt-synthesis technique" rather than conventional solid-state reaction techniques. Rapid synthesis methods to develop those double oxides have been strongly anticipated. During melt synthesis, the mixture of oxides or their precursors is melted rapidly (1-60 s) in an arc-imaging furnace using strong light radiation. A spherical molten sample with multiple homogeneously mixed cations was solidified directly on a copper hearth with rapid cooling of ca. 10(2) degrees C/s.
We studied the synthesis of A(2)BO(4) type double oxides (AA')(2)BO(4) (A= Sr(2+), Ca(2+), A' = La(3+), Gd(3+), Y(3+), Eu(3+), B=Al) using this method. Homogeneous samples with Eu(3+) dopants were synthesized using liquid phase mixing in a few seconds, which is much faster than diffusions of ions in solid phase. Red fluorescence under the irradiation of ultraviolet light (254 and 365 nm) was observed. The excitation band shifted. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jeurceramsoc.2009.05.040

Synthesis and Characterization of CaZnGe2O6 Reviewed

Hirotoshi Hatakeyama, Yousuke Narumi, Kazuyoshi Uematsu, Tadashi Ishigaki, Kenji Toda, Mineo Sato

ELECTROCERAMICS IN JAPAN XIII 445 187 - + 2010

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

We report the synthesis and photocatalytic activity of CaZnGe2O6, which contains Ca2+ ions and one-dimensional GeO4 chains (Ge4+: d(10) electronic configuration). This sample demonstrated the water splitting phenomenon by loading with RuO2 cocatalysis. Moreover, Ln-doped CaZnGe2O6 (where Ln = La, Ce, Pr, Nd, or Sm) shows a higher photocatalytic activity than CaZnGe2O6.

DOI： 10.4028/www.scientific.net/KEM.445.187

Development of New Red Phosphor Na3YSi2O7:Eu3+ for a white LED Reviewed

Shinichiro Kousaka, Kenji Toda, Tadashi Ishigaki, Kazuyoshi Uematsu, Mineo Sato

ASIAN CERAMIC SCIENCE FOR ELECTRONICS III AND ELECTROCERAMICS IN JAPAN XII 421-422 360 - + 2010

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

New red phosphors Na3YSi2O7:Eu3+ was prepared by a conventional solid-state reaction. This silicate phosphor can be efficiently excited by near UV light, yielding an intense red emission. Under the excitation of near UV light, the emission intensity is higher than that of a commercial red phosphor Y2O2S:Eu3+.

DOI： 10.4028/www.scientific.net/KEM.421-422.360

Luminescence Properties of Y(P,V)O-4 Synthesized by Microwave Heating Reviewed

Ayano Toda, Kenji Toda, Tadashi Ishigaki, Kazuyuki Uematsu, Mineo Sato

ASIAN CERAMIC SCIENCE FOR ELECTRONICS III AND ELECTROCERAMICS IN JAPAN XII 421-422 356 - + 2010

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

Eu3+ doped and undoped Y(P,V)O-4 phosphors were prepared using multi-mode and single-mode microwave oven operated at 2.45 GHz. In the case of the microwave heating method, the phosphor particles were non-aggregated. A homogeneous distribution of Eu ion was observed in the microwave synthesis. No sintering behavior found in the microwave heating may be attributed to a quite shorter heating time. The Eu3+ doped sample synthesized by microwave heating showed intense red emission under UV excitation.

DOI： 10.4028/www.scientific.net/KEM.421-422.356

Synthesis and luminescence properties of non-doped long persistent phosphors : Mg2SnO4 Reviewed

Akiko Torisaka, Hiroaki Kaneko, Kentaro Nomizu, Sho Abe, Tadashi Ishigaki, Kenji Toda, Kazuyoshi Uematsu, Mineo Sato

ASIAN CERAMIC SCIENCE FOR ELECTRONICS III AND ELECTROCERAMICS IN JAPAN XII 421-422 352 - + 2010

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

A white long persistence phosphor was synthesized in a single-phase of Mg2SnO4 which was synthesized by a solid-state reaction. This phosphor crystallized in an inverse spinel structure and showed a broad-band emission from 350nm to 700nm. The afterglow was observed upon the excitation by 254nm. A Li-doped Mg2SnO4 sample showed a higher photoluminescence intensity and a longer lifetime than the non-doped one.

DOI： 10.4028/www.scientific.net/KEM.421-422.352

Photocatalytic Activity of Bismuth Layered Perovskite Treated with Acid Reviewed

Soihiro Watanabe, Yousuke Narumi, Kenji Toda, Tadashi Ihigaki, Kazuyoshi Uematsu, Mineo Sato

ASIAN CERAMIC SCIENCE FOR ELECTRONICS III AND ELECTROCERAMICS IN JAPAN XII 421-422 554 - + 2010

Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

We synthesized Sr0.7La0.2[ ](0.1)Bi2Ta2O9 (SBTL, [ ] vacancy), and measured their photocatalytic activity for water decomposition under UV light irradiation after acid treatment. They showed the high photocatalytic activity under UV light irradiation (H-2 evolution (213 mu mol / h), O-2 evolution (82 mu mol / h)).

DOI： 10.4028/www.scientific.net/KEM.421-422.554

Novel Ba-Sc-Si-oxide and oxynitride phosphors for white LED Reviewed

Tomoyuki Nakano, Yoshitaka Kawakami, Kazuyoshi Uematsu, Tadashi Ishigaki, Kenji Toda, Mineo Sato

JOURNAL OF LUMINESCENCE 129 ( 12 ) 1654 - 1657 2009.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Alkaline earth silicates. which comprise a host material doped with rare-earth minerals, show excellent luminescence properties with various crystal structures and high stability. From results of this study, we report luminescence properties of Ba(9)Sc(2)Si(6)O(24):Eu(2+) and Ba(9)Sc(2+delta)Si(6)O(24+3 delta)N(3 delta):Eu(2+) as a novel alkaline earth silicate and silicon oxynitride phosphors for white LEDs Using a conventional solid-state reaction, Ba(9)Sc(2)Si(6)O(24):Eu(2+) samples were synthesized and Ba(9)Sc(2+delta)Si(6)O(24+3 delta)N(3 delta):Eu(2+) samples were obtained by nutrization of Ba(9)Sc(2+delta)Si(6)O(24):Eu(2+) The samples can be excited by blue light, exhibiting green (Ba(9)Sc(2)Si(6)O(24):Eu(2+)) and yellow (Ba(9)Sc(2+delta)Si(6)O(24+3 delta)N(3 delta):Eu(2+)) efficiently, which are emissions for use in white LEDs essentially. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jlumin.2009.04.028

Structure and luminescence of sodium and lanthanide(III) coordination polymers with pyridine-2,6-dicarboxylic acid Reviewed

Taoyun Zhu, Kazuya Ikarashi, Tadashi Ishigaki, Kazuyoshi Uematsu, Kenji Toda, Hirokazu Okawa, Mineo Sato

INORGANICA CHIMICA ACTA 362 ( 10 ) 3407 - 3414 2009.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

A series of coordination polymers constructed by sodium, lanthanide(III), and pyridine-2,6-dicarboxylate (dipic),NaLn(dipic)(2) center dot 7H(2)O (Ln = Eu, Gd, Tb), have been prepared under a hydrothermal condition. The crystal structures of the three compounds which are isostructual were determined by single-crystal X-ray diffraction. The two-dimensional layers found in the compounds are built up from six-folded {NaO(6)} polyhedra and nine-folded {LnN(2)O(7)} polyhedra, these being edge-shared each other along the c axis and bridged by carboxylate groups of dipic along the b axis, respectively. This two-dimensional framework provides cavities inside the layer and interlayer spaces outside the layer for accommodation of the two dipic molecules coordinated to a lanthanide(III) ions. The dehydrated materials obtained by heating the as-synthesized crystals at 200 degrees C held their crystal structure, and absorbed the same amounts of water molecules as those of the as-synthesized crystals upon the exposure of 100% relative humidity at room temperature. The Eu and Tb compounds showed strong red and green emissions, respectively, due to an energy transfer from dipic molecules to trivalent emission ions. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2009.01.036

One-dimensional coordination polymers of praseodymium(III)-vanadium(V) complexes with pyridine-2,6-dicarboxylic acid Reviewed

Taoyun Zhu, Koichi Murokawa, Kazuyoshi Uematsu, Tadashi Ishigaki, Kenji Toda, Hirokazu Okawa, Mineo Sato

POLYHEDRON 28 ( 11 ) 2196 - 2200 2009.7

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

This paper represents the hydrothermal synthesis of new isomorphous lanthanide-vanadium complexes with one-dimensional coordination polymers: [Pr(2)(VO(2))(2)(dipic)(4)(H(2)O)(9)] center dot nH(2)O with dipic = pyridine-2,6-dicarboxylic acid and n = 7.75. The structure determination shows a unique one-dimensional structure in which three types of chains run along the c-axis: the chain of positively charged praseodymium complexes bridged by a dipic ligand ([Pr(dipic)(H(2)O)5](+)), the chain of negatively charged, stacked vanadium complexes ([VO(2)(dipic)](-)), and the chain of neutral praseodymium complexes with a bridged dipic ligand and a coordinating dipic ligand ([Pr(dipic)[VO(2)(dipic)](H(2)O)(4)]). Such one-dimensional chains provide open channels which can accommodate water molecules. Not only accommodated water molecules but also ones coordinated to praseodymium ions were easily removed and absorbed upon heating at 200 degrees C and exposure of humidity at room temperature, respectively. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.poly.2009.01.010

Low Temperature Synthesis of TiO2 from Acid Solution Reviewed

S. Watanabe, S. Nkajima, K. Uematsu, T. Ishigaki, K. Toda, M. Sato

Key Engineering Materials 421-422 498 - 501 2009.7

New Titanium Oxide Compound for Photocatalytic Water Splitting, Hydrous Na16Ti10O28 Reviewed

S. Nakajima, S. Watanabe, K. Uematsu, T. Ishigaki, K. Toda, M. Sato

Key Engineering Materials 421-422 546 - 549 2009.7

One-dimensional channels constructed from hydrogen bonding networks among 4,4 '-bipyridine units and water molecules available for accommodation of polyoxomolybdate clusters Reviewed

Hidekazu Kobayashi, Kazuya Ikarashi, Kazuyoshi Uematsu, Kenji Toda, Hirokazu Okawa, Zhu Taoyun, Mineo Sato

INORGANICA CHIMICA ACTA 362 ( 1 ) 238 - 242 2009.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

A hybrid coordination complex, [(H(5)O(2))(H(2)bpy)(bpy)(4)][NaMo(8)O(26)]center dot 2H(2)O (bpy = 4,4-bipyridine), was synthesized via hydrothermal reactions at 150 degrees C. The structure consists of two moieties; one is an infinite chain of beta-[Mo(8)O(26)] clusters, each of which is inter-linked up by a sodium ion, and the other a two-dimensional network constructed from doubly protonated bpy ions and its neutral molecules, which are linked with water molecules by hydrogen bonds. The stacking of the networks provides one-dimensional tunnels suitable for Na-beta-[Mo(8)O(26)] chains. (c) 2007 Published by Elsevier B.V.

DOI： 10.1016/j.ica.2007.07.040

Metastable Sr0.5TaO3 Perovskite Oxides Prepared by Nanosheet Processing Reviewed

Keigo Inaba, Shinya Suzuki, Yuji Noguchi, Masaru Miyayama, Kenji Toda, Mineo Sato

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 2008 ( 35 ) 5471 - 5475 2008.12

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL

Metastable Sr0.5TaO3 with a perovskite structure was prepared by using layer-structured H2Sr1.5Ta3O10 by two different processes: direct dehydration and nanosheet processing, and the photocatalylic activities of the obtained structures were investigated for the evolution of H-2 and O-2 from distilled water under UV light irradiation. The average gas evolution rates were 66 mu mol h(-1) (H-2) and 1.6 mu mol h(-1) (O-2) for Sr0.5TaO3 prepared by direct dehydration, whereas those obtained by nanosheet processing were 1.26 mu mol h(-1) (H-2) and 33 mu mol h(-1) (O-2). It was shown that nanosheet processing is effective for obtaining metastable Sr0.5TaO3 with high photocatalytic activities. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

DOI： 10.1002/ejic.200800776

Morphology Cntrol of High Luminance Phosphors

K. Toda, M. Hosoume, K. Sato, K. Uematsu, M. Sato, A. watanabe, T. Fukui

Key Engineering Materilas 388 107 - 110 2008.7

Melt synthesis of oxide phosphors with K(2)NiF(4) structures: CaLa(1-x)Eu(x)GaO(4)

Tadashi Ishigaki, Kenji Toda, Tomoaki Watanabe, Naonori Sakamoto, Nobuhiro Matsushita, Masahiro Yoshimura

JOURNAL OF MATERIALS SCIENCE 43 ( 14 ) 4749 - 4752 2008.7

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

In order to synthesize compounds of various Perovskite-related structures, we have utilized a novel "melt synthesis technique" for phosphors rather than the conventional solid state reaction techniques. The solid state reactions require multi-step processes of heating/cooling with intermediate grindings to make homogeneous samples. However, for the melt synthesis, it is possible to make a homogeneous sample in a single step within a short period of time (1-60 s) due to the liquid phase reaction in the molten samples, which were melted by strong light radiation in an imaging furnace. In this study, we have prepared a red-phosphor CaLaGaO(4):Eu(3+) which has a perovskite-related layered K(2)NiF(4) structure. Well-crystallized CaLa(1-x) Eu (x) GaO(4) samples with the K(2)NiF(4) structure have been obtained up to x = 0.25, but there was the formation of an olivine phase when x = 0.5-1.0. The red emission at 618 nm increased with the increasing value of x up to x = 0.25.

DOI： 10.1007/s10853-008-2481-9

Synthesis and Luminescence Property of Blue Phosphor, BaMgAl<SUB>10</SUB>O<SUB>17</SUB>:Eu<SUP>2+</SUP>, by the Flash-Creation-Method

WATANABE Akira, FUKUI Takehisa, NOGI Kiyoshi, TODA Kenji, KAWADA Satoshi, SHIRAKURA Shigeki, HOSOUME Masafumi, UEMATSU Kazuyoshi, SATO Mineo

Journal of High Temperature Society Vol.34 ( 3 ) 130 - 135 2008.5

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：High Temperature Society of Japan

BaMgAl<SUB>10</SUB>O<SUB>17</SUB>:Eu<SUP>2+</SUP> is a promising blue phosphor for lump, CRT and PDP. Conventionally, the BAM phosphors synthesize by the solid-state reaction from the mixture of oxide or carbonate starting materials. The solid-state reaction needs high temperature to get well-crystallized single phase. However, the control of particle morphology and size distribution is difficult for such a high temperature synthesis. In this study, we reported new synthetic technique using flash creation method derived nanopowder precursor. In the new technique, well-crystallized single phase phosphors were obtained at 1400°C for 6h. Although the powders were grown into the plate-like particles, the BAM powders retain the nano-size morphology after annealing. The emission intensity under UV excitation of Ba<SUB>0.9</SUB>Eu<SUB>0.1</SUB>MgAl<SUB>10</SUB>O<SUB>17</SUB> from the FCM-derived nanopowder was 110% compared with phosphors prepared by the conventional solid-state reaction. The excitation intensity under VUV (146nm) of the FCM derived nanopowder was 159% of the conventional solid-state reaction.

DOI： 10.7791/jhts.34.130

Reinvestigation of layered poly[aqua-sodium(I) [[aquasamarium(III)]-di-mu-aqua-mu(3)-pyridine-2,6-dicarboxylato-mu(2)-pyridine-2,6-dicarboxylato] trihydrate]

Kazuya Ikarashi, Taoyun Zhu, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE 63 ( 8 ) M2203 - U1635 2007.8

Language：English Publishing type：Research paper (scientific journal) Publisher：BLACKWELL PUBLISHING

The crystal structure of the title compound, {[NaSm(C7H3- NO4)(2)(H2O)(4)]center dot 3H(2)O}(n), was first reported by van Albada, Gorter & Reedijk [(1999), Polyhedron, 18, 1821-1824]. It has now been reinvestigated and confirmed from single-crystal data, giving greater understanding of the role of the water molecules. The two-dimensional layers found in the compound are built up from six-coordinate NaO6 polyhedra and nine-coordinate SmN2O7 polyhedra. The former share edges with each other along the c axis and the latter are bridged by carboxylate groups of pyridine-2,6-dicarboxylate anions along the b axis. Eight-membered rings of water molecules, connected to one another by hydrogen bonding, are formed in the interlayer spaces.

DOI： 10.1107/S160053680702884X

Lanthanum-indium oxysulfide as a visible light driven photocatalyst for water splitting Reviewed

Kiyonori Ogisu, Akio Ishikawa, Kentaro Teramura, Kenji Toda, Michikazu Hara, Kazunari Domen

CHEMISTRY LETTERS 36 ( 7 ) 854 - 855 2007.7

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

La-In-based oxysulfide is demonstrated to act as a photocatalyst for the reduction of H+ to H-2 and the oxidation of H2O to O-2 in the presence of sacrificial reagents under visible light (420 < A < 480 nm). Loading with IrO2 is effective for promoting O-2 evolution, while Pt is effective as a cocatalyst for H-2 evolution.

DOI： 10.1246/cl.2007.854

Solid Chemical Reaction by Microwave Heating for the Synthesis of LiFePO4 Cathode Material Reviewed

K.. Uematsu, A. Ochiai, K. Toda, M. Sato

Journal of Ceramic Society of Japan 115 ( 7 ) 450 - 454 2007.7

Superconductivity of Layered Perovskite Synthesized by Soft Chemistry Reviewed

T. Teranishi, S. Takezawa, K. Toda, H. Ishikawa, K. sato, K. Uematsu, M. Sato

Key Engineering Materials 350 163 - 166 2007.6

Electrochemical performance of Al-doped LiMn2O4 prepared by different methods in solid-state reaction Reviewed

Teruaki Kakuda, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

JOURNAL OF POWER SOURCES 167 ( 2 ) 499 - 503 2007.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Al-doped LiMn2O4 cathode materials synthesized by a newly developed wet-milling method and a dry process method using a conventional solid-state reaction were evaluated physicochemically and electrochemically. In the wet-milling method, a precursor was made from the raw materials atomized by a wet milling. A good cyclic performance was obtained for the LiMn2O4 samples prepared by the wet-milling method, achieved up to 99% of retention of capacity at 50 degrees C at the 30th cycle. The precursor obtained by the wet-milling method was well homogenous and highly reactive due to their finely ground particles, giving good crystallinity to LiMn2O4 products. (C) 2007 Published by Elsevier B.V.

DOI： 10.1016/j.jpowsour.2007.01.035

Synthesis of Blue Phosphor, BaMgAl10O17: Eu2+, from the Flash Creation Method Derived Nanopowder Reviewed

A. Watanabe, T. Fukui, Y. Ito, M. Hosoume, S. Shirakura, S. Kawada, K. Toda, K. Uematsu, M. Sato

ITE LETTERS 8 ( 1 ) 38 - 41 2007.2

透光性酸化イットリウム(Y2O3)焼結体の作製 Reviewed

齋藤紀子, 渡邊良二, 瀬山博之, 戸田健司, 大滝浩通, 堀田憲康

Journal of the Materials Science Society of Japan 44 ( 1 ) 272 - 277 2007.2

Origin and model for cooperative host-guest interaction affecting the orientation of guests in oriented nematic hosts Reviewed

Michio Kobayashi, Ken-ichi Kumagai, Toshihiko Hoshi, Takuya Yamaguchi, Hirobumi Sato, Kenji Toda, Yoshie Tanizaki, Tetsutaro Yoshinaga

MOLECULAR CRYSTALS AND LIQUID CRYSTALS 469 31 - 49 2007

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

It has been observed for the binary systems of oriented nematic hosts and nonmesomorphic guests (substituted anthraquinones) that the orientational orders of amino-substituted anthraquinones ascend with increasing guest concentrations. A new quantitative anti experimental procedure has been proposed for obtaining the host-guest isotropic dispersion, isotropic electrostatic, anisotropic dispersion, and anisotropic electrostatic interaction energies. Among these four host-guest interaction energies, the host-guest isotropic dispersion interaction energy alone is demonstrated to be well correlated with the concentration dependence of the orientational order of the guest. A model is also proposed for the cooperative and isotropic host-guest interaction.

DOI： 10.1080/1542140070143187

Removal of Fluorinefrom Waste Water by Ettringite Reviewed

T. Tokumitsu, K. Toda, H. Morinaga, K. Sato, K. Uematsu, M. Sato

ITE LETTERS 7 352 - 355 2006.12

Self Assemble Synthesis of Potassium Niobate at Room Temperature Reviewed

K. Toda, A. Sugawara, K. Uematsu, M. Sato, M. Osada

Key Engineering Materials 320 7 - 10 2006.12

New silicate phosphors for a white LED Invited Reviewed

Kenji Toda, Yoshitaka Kawakami, Shin-ichiro Kousaka, Yutaka Ito, Akira Komeno, Kazuyoshi Uematsu, Mineo Sato

IEICE TRANSACTIONS ON ELECTRONICS E89C ( 10 ) 1406 - 1412 2006.10

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

We focus on the development of new silicate phosphors for a white LED. In the europium doped silicate system, four LED phosphor candidates-Li2SrSiO4:Eu2+, Ba9Sc2Si6O24:Eu2+, Ca3Si2O7:Eu2+ and Ba2MgSi2O7:Eu2+ were found. Luminescent properties under near UV and visible excitation were investigated for the new Eu2+ doped LED silicate phosphors. These new phosphors have a relatively strong absorption band in a long wavelength region.

DOI： 10.1093/ietele/e89-c.10.1406

Development of an open-ended coaxial line probe for measurement of dielectric properties of inorganic materials at high temperature Reviewed

Kazuyoshi Uematsu, Jyunji Tsuchida, Mineo Sato, Kenji Toda

JOURNAL OF THE AMERICAN CERAMIC SOCIETY 89 ( 8 ) 2638 - 2640 2006.8

Language：English Publishing type：Research paper (scientific journal) Publisher：BLACKWELL PUBLISHING

An open-ended coaxial line probe for dielectric measurements at high temperatures was developed. The probe, which was fabricated using stainless steel as the center and outer conductors and quartz wool as an insulator, can function well up to 800 degrees C. The dielectric properties of the raw materials and resultant materials were measured using a network analyzer that was equipped with the open-ended coaxial line probe at high temperatures to clarify the formation reaction process of YVO4:Eu3+ and Mg2SnO4:Mn2+ phosphors using a microwave heating method. The developed probe was confirmed to be effective for reaction-process analyses at high temperatures.

DOI： 10.1111/j.1551-2916.2006.01074.x

Luminescence properties of long-persistence silicate phosphors Reviewed

Y Ito, A Komeno, K Uematsu, K Toda, M Sato

JOURNAL OF ALLOYS AND COMPOUNDS 408 907 - 910 2006.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Tb3+-doped and (Ce3+, Tb3+)-codoped Ca0.5Sr1.5Al2SiO7 were prepared using a solid-state reaction at 1273 K for 3 h in air and 1623 K for 6 h in a weakly reductive atmosphere of 5% H-2-95% N-2 gas. The resultant (Ce3+, Tb3+)-codoped Ca0.5Sr1.5Al2SiO7 phosphor shows four main emission peaks: one at 386 run for Ce3+ and three at 483, 542 and 591 nm for Tb3+. Emission intensity of Tb3+ in the (Ce3+, Tb3+)-codoped phosphor was five times greater than that of the Tb3+ single-doped phosphor because of the energy transfer from Ce3+ to Tb3+. The codoped phosphor showed long-persistence white phosphorescence. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2005.01.132

VUV phosphors in the SrO-B2O3-P2O5 ternary system Reviewed

Y Komatsu, A Komeno, K Toda, K Uematsu, M Sato

JOURNAL OF ALLOYS AND COMPOUNDS 408 903 - 906 2006.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Photoluminescence properties under vacuum ultraviolet (VUV, 147 nm) excitation were investigated for a new borophosphate compound. The new phosphor, Sr6BP5O20, has a relatively strong absorption band in a short wavelength region because of the strong covalent characters of B-O and P-O bonds. The phosphor activated by Eu2+ showed a strong blue luminescence. The luminance is about 2.2 times as bright as a commercial blue phosphor, BaMgAl10O17:Eu2+. The phosphor is an attractive candidate of new phosphors for plasma display panels and mercury-free fluorescent lamps. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2005.01.098

Recent research and development of VUV phosphors for a mercury-free lamp Reviewed

K Toda

JOURNAL OF ALLOYS AND COMPOUNDS 408 665 - 668 2006.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

This study specifically addresses development of new inorganic oxide phosphors for a Xe-discharge mercury-free lamp. We describe the relationship between the luminescence property under vacuum ultraviolet (VUV) excitation and the crystal structure of new VUV phosphors. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2005.01.080

VUV properties of Eu-doped alkaline earth magnesium silicate Reviewed

A Komeno, K Uematsu, K Toda, M Sato

JOURNAL OF ALLOYS AND COMPOUNDS 408 871 - 874 2006.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Plasma display panels (PDP) are most promising for large flat panel displays at present. However, luminescence efficiency and lifetime of PDP phosphors should be improved. Alkaline earth silicates show remarkable properties as phosphor hosts with various crystal structures and high chemical stability. Availability of Ba2MgSi2O7 has received attention as a host for vacuum ultraviolet (VUV) excitable phosphor. Blue-green phosphor Ba2MgSi2O7:Eu2+ with a high thermal quenching temperature [G. Blasse, W.L. Wanmaker, J.W. ver Vrugt, A. Bril, Philips. Res. Rep. 23 (1968) 189-200] exhibit high luminance (45% of commercial green VUV phosphor Zn2SiO4:Mn2+) under VUV excitation without optimization of synthesis condition and emission color. Ba2MgSi2O7 is promising candidate for the new VUV phosphor in PDP and mercury-free lamp application. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2005.01.070

Characterization of YVO4 : Eu3+ phosphors synthesized by microwave heating method Reviewed

K Uematsu, A Ochiai, K Toda, M Sato

JOURNAL OF ALLOYS AND COMPOUNDS 408 860 - 863 2006.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

YVO4:Eu3+ phosphors were prepared using a domestic microwave oven operated at 2.45 GHz with 500 W. The temperature of raw materials with mixtures of Y2O3, V2O5 and Eu2O3 that were irradiated with the microwave increased to about 840 degrees C within 150 s. Subsequently, the temperature dropped sharply in spite of the continuing microwave irradiation. Measurement of the dielectric loss factor of the raw materials and products at 2.45 GHz at temperatures from 25 degrees C to 800 degrees C revealed a high absorption efficiency of microwave energy by V2O5, which provided a rapid increase in the raw material's temperature. A low dielectric loss factor observed for YVO4:Eu engendered a sharp temperature drop after completion of the reaction of Y2O3 with V2O5, (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2005.01.081

Luminescent properties of red long persistence phosphors, BaMg2Si2O7 : Eu2+, Mn2+ Reviewed

S Abe, K Uematsu, K Toda, M Sato

JOURNAL OF ALLOYS AND COMPOUNDS 408 911 - 914 2006.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Long persistence phosphors of BaMg2Si2O7:Eu2+, Mn2+, with red emission were prepared using a conventional solid state reaction. Phosphors doped only With Eu2+ emitted 1400 nm violet light; those doped only with Mn2+ emitted red light that was hardly visible. Phosphors doped with both Eu2+ and Mn2+ showed two emission peaks of 400 and 660 nm, exhibiting a reddish luminescence to the naked eye. These facts suggested an energy transfer from Eu2+ to Mn2+. Non-stoichiometric co-doped phosphors with a deficient Ba component showed long persistence phosphorescence with reddish color. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2005.03.092

Powder neutron diffraction study of layered perovskite, KCa 2Nb3O10 Reviewed

Toshiaki Tokumitsu, Kenji Toda, Tsukuru Aoyagi, Daiki Sakuraba, Kazuyoshi Uematsu, Mineo Sato

Journal of the Ceramic Society of Japan 114 ( 1333 ) 795 - 797 2006

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

Crystal structure of a layered perovskite, KCaiNbjOm, was determined by the Rietveld refinement method for a powder neutron diffraction pattern. The compound crystallizes a monoclinic system with a space group P21/m (No. 11) and lattice parameters of a = 0.77418 (6) nm, 6 = 0.77073(6) nm, c = 1.4859(1) nm, β = 97.51(1)°.

DOI： 10.2109/jcersj.114.795

Removal of fluoride from aqueous solution by ettringite Reviewed

Toshiaki Tokumitsu, Kenji Sato, Kenji Toda, Hiroko Morinaga, Kazuyoshi Uematsu, Mineo Sato

Journal of the Ceramic Society of Japan 114 ( 1332 ) 729 - 732 2006

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

In order to purify waste water containing fluoride, the calcium additive method has usually been used to recover fluoride ions in the form of refractory calcium fluoride. In this case, the removable fluoride concentration is limited to be 10-15 mg/1 due to the solubility of calcium fluoride. In this study, we report 3CaO·Al2O3·3CaSO4· 32H2O (ettringite) as a highly absorbent substance for the fluoride. The fluoride concentration of the water treated with the ettringite was achieved to be less than 8 mg/l without sludge.

DOI： 10.2109/jcersj.114.729

Possibility of superconductivity in a layered perovskite niobate, KCa 2Nb3O10, synthesized by an ion exchange reaction Reviewed

Sachi Takezawa, Takashi Teranishi, Hironori Ishikawa, Toshiaki Tokumitsu, Kenji Toda, Kazuyoshi Uematsu, Mineo Sato

Journal of the Ceramic Society of Japan 114 ( 1334 ) 861 - 865 2006

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

We prepared low temperature phase of triple layered perovksite KCa 2Nb3O10 by an ion-exchange reaction. Liintercalated low temperature phase, Li0.79KCa2Nb 3O10, shows strong diamagnetic signal around at 7.8 K. The magnetic phase transition temperature of Li-intercalated low temperature phase is higher than that of Li-interca-lated high temperature phase.

DOI： 10.2109/jcersj.114.861

Synthesis of KNbO3 thin film by self-assembly of perovskite nanosheets Reviewed

A. Sugawara, K. Uematsu, K. Toda, M. Sato

Transactions of the Materials Research Society of Japan 30 583 - 586 2005.12

Synthesis of Thin Film by Self-Assembly of Perovskite Nanosheets Reviewed

A. Sugawara, K. Uematsu, K. Toda, M. Sato

Key Engineering Materials 301 99 - 102 2005.12

長残光蛍光体Sr2MgSi2O7:Eu,Dyのゾルゲル合成 Reviewed

白倉重樹, 戸田健司, 今成裕一郎, 野々川貴志, 上松和義, 佐藤峰夫, 西須佳宏, 小林幹男

Journal of Ceramic Society of Japan 113 442 - 445 2005.12

Synthesis of Nitride Compounds Using Fluidized Bed Reviewed

Y. Yamanaka, K. Toda, T. Matsumoto, K. Uematsu, M. Sato, N. Hotta

Key Engineering Materials 301 231 - 234 2005.12

Self-Assembly of Perovskite Nanosheet Colloid at Room Temperature Reviewed

K. Toda, H. Sato, A. Sugawara, S. Tokuoka, K. Uematsu, M. Sato

Key Engineering Materials 301 227 - 230 2005.12

Al粉末の浮上式窒化反応によるAlN微粉末の合成と表面改質 Reviewed

堀田憲康, 橋本賢太, 戸田健司, 鷲山宏治, 堀田幹則, 北條純一

Journal of the Materials Science Society of Japan 42 ( 5 ) 272 - 277 2005.12

New Tantalum Oxynitride Photocatalyst Reviewed

K. Toda, Y. Yamanaka, T. Matsumto, H. Sato, K. Uematsu, M. Sato, N. Hotta

Transactions of the Materials Research Society of Japan 30 465 - 468 2005.12

New Phosphors for Mercury-free Illumination Reviewed

K. Toda, Y. Ito, M. Kawamoto, Y. Komatsu, A. Komeno, K. Uematsu, M. Sato

Transactions of the Materials Research Society of Japan 30 433 - 436 2005.12

Ionic Conductivity of Layered Borate (NaxBa1-x/2)Al2B2O7 Reviewed

A. Komeno, Y. Aoyama, K. Uematsu, K. Toda, M. Sato

ITE LETTERS 6 331 - 334 2005.12

Overall water splitting on (Ga1-xZnx)(N1-xOx) solid solution photocatalyst: Relationship between physical properties and photocatalytic activity Reviewed

K Maeda, K Teramura, T Takata, M Hara, N Saito, K Toda, Y Inoue, H Kobayashi, K Domen

JOURNAL OF PHYSICAL CHEMISTRY B 109 ( 43 ) 20504 - 20510 2005.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The physical and photocatalytic properties of a novel solid solution between GaN and ZnO, (Ga1-xZnx)(Ni1-xOx), are investigated. Nitridation of a mixture of Ga2O3 and ZnO at 1123 K for 5-30 h under NH3 flow results in the formation of a (Ga1-xZnx)(N1-xOx) solid solution with x = 0.05-0.22. With increasing nitridation time, the zinc and oxygen concentrations decrease due to reduction of ZnO and volatilization of zinc, and the crystallinity and band gap energy of the product increase. The highest activity for overall water splitting is obtained for (Ga1-xZnx)(N1-xOx) with x = 0.12 after nitridation for 15 h. The crystallinity of the catalyst is also found to increase with increasing the ratio of ZnO to Ga2O3 in the starting material, resulting in an increase in activity.

DOI： 10.1021/jp053499y

Photocatalytic water splitting on Ni-intercalated Ruddlesden-Popper tantalate H2La2/3Ta2O7 Reviewed

K Shimizu, S Itoh, T Hatamachi, T Kodama, M Sato, K Toda

CHEMISTRY OF MATERIALS 17 ( 20 ) 5161 - 5166 2005.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

A series of Ruddlesden-Popper-type hydrous layered perovskites, A'(2)ATa(2)O(7) (A' = H or K, A = La-2/3 or Sr), were presented as novel catalysts for photocatalytic water splitting into H-2 and O-2 under UV irradiation. These hydrous perovskites showed higher activity than anhydrous perovskites (KTaO3, La1/3TaO3) for overall splitting of water. Results of photoluminescence spectroscopy and H-2 evolution from aqueous n-butylamine solution support the hypothesis that the high activity of the hydrous perovskites results from their hydrated layered structure, where the photogenerated electrons and holes can be effectively transferred to the intercalated substrates (H2O and n-butylamine). Addition of Ni cocatalyst to H2La2/3Ta2O7 via an ion-exchange reaction increased the activity, while Ni addition did not improve the activity of H2SrTa2O7. Ni K-edge EXAFS/XANES, UV-vis spectroscopy, and TEM results for Niloaded catalysts indicate that Ni2+ ions and small NiO clusters are intercalated into the layers of H2La2/3Ta2O7, while relatively large NiO particles at the external surface of the perovskite are the main Ni species in H2SrTa2O7. Thus, the highly dispersed Ni(II) species at the interlayer space are shown to act as effective sites for H-2 evolution in the photocatalytic water splitting.

DOI： 10.1021/cm050982c

Preparation of KNbO3 thin film by self-assembly of perovskite nanosheet Reviewed

K Toda, A Sugawara, K Uematsu, M Sato

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44 ( 9B ) 6973 - 6976 2005.9

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN SOC APPLIED PHYSICS

Potassium niobate thin films with a perovskite structure were prepared by a new nanosheet self-assembly technique on a SiO2 glass substrate. A homogeneous nanosheet precursor solution was obtained by dissolving layered perovskite K2NbO3F in water at room temperature without any modifier. It was confirmed by X-ray diffraction that the films have a pseudocubic perovskite structure and show continuous transformation from layered perovskite K2NbO3F to perovskite KNbO3. The ultraviolet-vi sib le absorption spectra of the films showed an increase in absorbance with the thickness of thin films, suggesting the growth of a self-assembled multilayer consisting of perovskite nanosheets and K+ ions.

DOI： 10.1143/JJAP.44.6973

Photocatalytic performance of Ba5Ta4O15 to decomposition of H2O into H-2 and O-2 Reviewed

H Otsuka, KY Kim, A Kouzu, Takimoto, I, H Fujimori, Y Sakata, H Imamura, T Matsumoto, K Toda

CHEMISTRY LETTERS 34 ( 6 ) 822 - 823 2005.6

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

The photocatalytic performance of barium tantalates in the decomposition of H2O into H-2 and O-2 was investigated. Ba5Ta4O15 that was prepared under Ta rich atmosphere exhibited remarkable photocatalytic activity. Under the same reaction conditions, its activity was the highest among all of the alkali earth-tantalum mixed-oxide photocatalysts prepared.

DOI： 10.1246/cl.2005.822

Preparation of YVO4 : Eu3+ phosphor using microwave heating method Reviewed

K Uematsu, K Toda, M Sato

JOURNAL OF ALLOYS AND COMPOUNDS 389 ( 1-2 ) 209 - 214 2005.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

YVO4:Eu3+ phosphor was prepared using a domestic microwave oven operated at a frequency of 2.45 GHz and a power of 500 W. The temperature of raw materials, mixtures of Y2O3, V2O5 and Eu2O3, irradiated with the microwave was rose up to about 1113 K in 150 s, followed by a sharp drop in the temperature in spite of irradiating the microwave continuously. From the measurement of a dielectric loss factor of the raw materials at 2.45 GHz, a high absorption of microwave energy by V2O5 was found to provide an increase in temperature of the mixture. On the other hand, a low dielectric loss factor of YVO4 caused the sharp drop in temperature as soon as the reaction of Y2O3 with V2O5 was completed. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2004.05.083

Synthesis and luminescence properties of new long persistent phosphors. Reviewed

A. Komeno, Y. Ito, S. Abe, K. Uematsu, K. Toda, M. Sato

TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN, VOL 30, NO 4 30 ( 4 ) 1053 - 1056 2005

Language：English Publishing type：Research paper (international conference proceedings) Publisher：ELSEVIER SCIENCE BV

Long persistent phosphors are materials which can absorb visible light energy to show afterglow. Previously, alkaline earth metal sulfides and zinc sulfides doped radioactive materials were used for the long persistent phosphors. However, sulfides tend to deteriorate upon expose of moisture in air. On the other hand, though the radio luminous phosphors give long afterglows, radioactive materials have serious influence on environment. The highly stable and highly luminescent long persistent phosphors without radioactive materials are desired.
In this study, silicate families were chosen as hosts because of their excellent physical and chemical stability. The Ca0.5Sr1.5Al2SiO7: Ce3+, Tb3+ phosphor showed the fluorescence of 5 times as high radiation intensity as the Ce3+ single-doped phosphor. The cause is energy migration from Ce3+ to Tb3+. The co-doped phosphor showed white long-persistent phosphorescence. The non-stoichiometric BaMg2Si2O7: Eu2+ Mn2+ phosphors with a Ba-deficient component exhibiting a long persistent phosphorescence with reddish color with two emission peaks of 400 mn and 660 nm. The cause is energy migration from Eu2+ to Mn2+. The afterglows of these long persistent phosphors are occurred by sensitization between co-doped ions.

Synthesis of phosphor materials using silica sand Reviewed

Takashi Nonogawa, Yu-Ichiro Imanari, Kenji Toda, Shigeki Shirakura, Kazuyoshi Uematsu, Mineo Sato, Ayano Toda, Yoshihiro Nishisu, Mikio Kobayashi

Journal of the Ceramic Society of Japan 113 ( 1318 ) 442 - 445 2005

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

The silica sand is primarily composed of high purity SiO2. Mt. Iide over Niigata, Yamagata and Fukushima prefectures is known as a rich mine for silica sand. In this study, we adopted natural resource (silica sand from Mt. Iide, Osodani area) as a starting material for the synthesis of akermanite type long-persistent phosphor Sr2MgSi2O7: Eu2+, Dy3+. The silica sand derived (Sr 0.98Eu0.01Dy0.01)2MgSi 2O7 showed long afterglow phenomena. Therefore, the silica sand can be potentially used in preparing silicate phosphors.

DOI： 10.2109/jcersj.113.442

Combinatorial screening and QSAR modeling in the SrO-B2O3-P2O5 ternary system to search for thermally stable blue phosphors for PDPs Reviewed

KS Sohn, JG Yoo, N Shin, K Toda, DS Zang

JOURNAL OF THE ELECTROCHEMICAL SOCIETY 152 ( 12 ) H213 - H218 2005

Language：English Publishing type：Research paper (scientific journal) Publisher：ELECTROCHEMICAL SOC INC

The need to identify a thermally stable blue phosphor for plasma display panels (PDPs) is vital, because the currently used BaMgAl10O17:Eu2+ (BAM) phosphors have serious thermal degradation problems. In this respect, we report on the screening of a Eu2+-doped SrO-B2O3-P2O5 system by a combinatorial chemistry technique so that combinatorial libraries could be developed in terms of luminance and color chromaticity. As a quantitative structure activity relationship (QSAR) model, a continuous luminance map was obtained as a function of composition using an artificial neural network trained using the results from the combinatorial screening. Promising photoluminescence was found in a lineshape composition range in the SrO-B2O3-P2O5 ternary library, and the samples in this composition range were crystallized into a single major phase of Sr6BP5O20:Eu2+ in an I $(4) over bar $ c2 symmetry with cell parameters a=9.784 and c=19.01. The luminance of Sr6BP5O20:Eu2+ was 2.8 times as high as BAM under vacuum ultraviolet (VUV) excitation and underwent negligible thermal degradation, even though the CIE color chromaticity was somewhat poor. (c) 2005 The Electrochemical Society. All rights reserved.

DOI： 10.1149/1.2083208

Synthesis of nitride compound using fluidized bed Reviewed

Yoshiomi Yamanaka, Kenji Toda, Kazuyoshi Uematsu, Mineo Sato, Noriyasu Hotta

Transactions of the Materials Research Society of Japan, Vol 30, No 4 30 ( 4 ) 1089 - 1092 2005

Language：English Publishing type：Research paper (international conference proceedings) Publisher：ELSEVIER SCIENCE BV

Compositionally uniformed nitride powders (GaN and GaN-ZnO solid solution) were synthesized from metal oxide powders using a fluidized bed in a NH3 and/or a N-2 flow. GaN was synthesized by a two-step heating; the first step was done at 700 degrees C for 1 h, and the second step was done at 900 degrees C for 4h. A GaN-ZnO solid solution was synthesized at 900 degrees C for 4h. The synthesized nitride powders were characterized by powder X-ray diffraction (XRD). Optical properties of the products were examined by UV-Vis diffuse reflectance spectra. The grain size of the products was smaller than that of the starting materials. On the other hand, the crystallite size of the GaN-ZnO solid solution was almost the same as that of the starting material of Ga2O3.

Preparation of KNbO3 Nanoparticles at Room Temperature Reviewed

K. Toda, H. Sato, A. Sugawara, S.Tokuoka, K. Uematsu, M. Sato, A. A. Bokov, Z-G. Ye

Key Engineering Materials 269 165 - 168 2004.12

Influence of High-Temperature Treatment of Silica Gel and Porous Glass on Concentration of Tritiated Water by Adsorption Method Reviewed

UEMATSU Kazuyoshi, TODA Kenji, SATO Mineo

RADIOISOTOPES 53 ( 8 ) 435 - 443 2004.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Radioisotope Association

<I>Silica gels and porous glasses thermally treated at various temperatures were examined for use as an adsorbent to separate tritiated water</I> (HTO) <I>with an adsorption method. The</I> HTO <I>was adsorbed much stronger than</I> H<SUB>2</SUB>O. <I>A high partition coefficient of 1.38 was observed for the thermally treated silica gel at 1100°C in vacuo. From the measurement of</I> IR <I>spectra, isolated silanol groups were formed on the thermally treated silica gel surface. We can conclude that there is a large mass effect for the concentration of tritiated water on the thermally treated silica gels because hydroxyl groups or water molecules adsorbed on them are difficult to form hydrogen bonds with each other.</I>

DOI： 10.3769/radioisotopes.53.435

Colloid Chemistry of Layered Perovskite Niobate Reviewed

K. Toda, K. Shimizu, H. Sato, A. Sugawara, K. Uematsu, M. Sato

Transactions of the Materials Research Society of Japan 29 2399 - 2402 2004.12

Structural Characterization of Bismuth Layered Perovskite Treated with Acids Reviewed

T. Aoyagi, K. Toda, K. Uematsu, M. Sato

Key Engineering Materials 269 181 - 184 2004.12

Structure Analysis of A-Site Defect Perovskite-Type Crystal Reviewed

A. Komeno, Y. Aoyama, K. Toda, M. Sato, K. Uematsu

Key Engineering Materials 269 11 - 14 2004.12

Mechanoluminescen Phenomenon of Niobates Reviewed

D. Sakuraba, K. Toda, K. Uematsu, M. Sato

Key Engineering Materials 269 99 - 104 2004.12

Enhanced electrochemical performance of LiFePO4 prepared by hydrothermal reaction Reviewed

S Tajimi, Y Ikeda, K Uematsu, K Toda, M Sato

SOLID STATE IONICS 175 ( 1-4 ) 287 - 290 2004.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Well-crystalline LiFePO4 particles were prepared by a hydrothermal reaction. The particles thus prepared by adding polyethylene glycol (PEG) to the starting reaction solution were fine crystalline in the range of 0.5-1.5 mum with a narrow particle size distribution. The initial discharge capacity of the sample as a lithium secondary battery was achieved to 143 mAhg(-1) at 0.5 mA cm(-2) (corresponding to 35 mA g(-1)) larger than that of the sample prepared by the hydrothermal method without PEG. The increase in the initial discharge capacity should be correlated with the change in particle size and degree of crystallization. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2003.12.033

Intelligent reactions of inorganic phosphor materials with microwave heating Reviewed

K Uematsu, K Toda, M Sato

CHEMISTRY LETTERS 33 ( 8 ) 990 - 991 2004.8

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

YVO4:Eu3+ and Mg2SnO4:Mn2+ phosphors were prepared using a domestic microwave oven. The temperature of the raw materials irradiated with a microwave was rose up to 1111-1716 K within 150 s, followed by a sharp drop in the temperature in spite of irradiating the microwave continuously. A low dielectric loss factor of the reaction products caused the sharp drop in temperature as soon as the reaction was completed.

DOI： 10.1246/cl.2004.990

Photocatalytic water splitting on hydrated layered perovskite tantalate A(2)SrTa(2)O(7)center dot nH(2)O ( A = H, K, and Rb) Reviewed

K Shimizu, Y Tsuji, T Hatamachi, K Toda, T Kodama, M Sato, Y Kitayama

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 6 ( 5 ) 1064 - 1069 2004

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

A series of layered perovskite tantalates, A(2)SrTa(2)O(7) (A=H, Li, K, and Rb), were prepared as novel photocatalysts for photocatalytic water splitting into H-2 and O-2 under UV irradiation. The layered perovskite tantalates with hydrated interlayer space, A(2)SrTa(2)O(7).nH(2)O (A=H, K, and Rb), showed higher H-2 formation rate than anhydrous layered tantalate, Li2SrTa2O7, and anhydrous perovskite tantalate, KTaO3. H2SrTa2O7.nH(2)O and K2SrTa2O7.nH(2)O showed high activity for overall splitting of water without loading co-catalysts. The reaction over H2SrTa2O7.nH(2)O proceeded steadily more than 70 h, demonstrating a high durability of the catalyst. Effects of hydrated interlayer space on the catalytic activity were discussed on the basis of the results of photoluminescence spectra and the hydrogen evolution from aqueous solution of n-butylamine as a test reaction. The results indicate that the availability of interlayer space of layered tantalate as reaction sites is an important factor to improve the photocatalytic activity of Ta-based semiconductor materials.

DOI： 10.1039/b312620j

セルフラックス法による真空紫外励起蛍光体の合成 Reviewed

稲田直樹, 戸田健司, 上松和義, 佐藤峰夫, 西須佳宏, 小林幹男

Journal of Ecotechnology Research 9 143 - 147 2003.12

Characterization of Phosphors in the Eu-doped Sr-Al-B-O system Reviewed

MIYOSHI Jun-ichi, TODA Kenji, UEMATSU Kazuyoshi, SATO Mineo, NISHISU Yoshihiro, KOBAYASHI Mikio

J.Ecotech.Res 9 ( 2 ) 137 - 142 2003.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Association of Ecotechnology Research

Phosphor materials have been searched in the Sr-Al-B-O system. For a molar ratio (Sr<SUB>1-x</SUB>Eu<SUB>x</SUB>) : Al : B = 1 : 2 : 2 (x = 0.01), a crystalline layered compound SrAl<SUB>2</SUB>B<SUB>2</SUB>O<SUB>7</SUB>：Eu<SUP>2+</SUP> was synthesized at 900 °C for 12 h in a reductive atmosphere. The SrAl<SUB>2</SUB>B<SUB>2</SUB>O<SUB>7</SUB>:Eu<SUP>2+</SUP> showed blue emission under UV (254 nm) and VUV (Vacuum Ultraviolet, 146 nm) excitation. For the ratio (Sr<SUB>1-x</SUB>Eu<SUB>x</SUB>) : Al : B = 2 : 2 : 2 (x = 0.01), a transparent glass and SrAl<SUB>2</SUB>O<SUB>4</SUB> component with a long afterglow phosphorescence was found.

DOI： 10.11190/jer.9.137

Other Link： https://jlc.jst.go.jp/DN/JLC/20007068193?from=CiNii

Research and Characterization of the Phosphor for Mercury-free Fluorescent Lamps Reviewed

K. Toda, Y. Imanari, T. Nonogawa, K. Uematsu, M. Sato

Transactions of the Materials Research Society of Japan 28 1247 - 1250 2003.12

Synthesis of KNbO3 in Water Reviewed

K. Toda, S. Tokuoka, N. Ohtake, K. Uematsu, M. Sato

Transactions of the Materials Research Society of Japan 28 353 - 356 2003.12

Reaction Mechanism of Perovskite KNbO3 in Aqueous Solution Reviewed

K. Toda, S. Tokuoka, N. Ohtake, K. Uematsu, M. Sato

Key Engineering Materials 248 27 - 30 2003.12

Low Temperature Synthesis of Titanium oxide Reviewed

K. Toda, M. Kawakami, K. Uematsu, M. Sato

Transactions of the Materials Research Society of Japan 28 313 - 316 2003.12

Low Temperature Synthesis of Titania and Titanates Reviewed

K. Toda, M. Kawakami, K. Uematsu, M. Sato

Key Engineering Materials 248 107 - 110 2003.12

Green VUV phosphor with spinel structure, Mg1-xZnxAl2-yGayO4:Mn Reviewed

K. Toda, Y. Imanari, R. Arai, K. Uematsu, M. Sato, K. Ohno, S. Miyazaki

Journal of Materials Science Letters 22 ( 13 ) 979 - 980 2003.7

Language：English Publishing type：Research paper (scientific journal)

A green-emitting vacuum ultraviolet (VUV) phosphor, Mg1-xZnxal2-y-gayO4:Mn was synthesized by the conventional solid state reaction. The composition, Mg0.88Zn0.10Mn0.02Al2O4, shows the highest brightness under VUV excitation, which corresponds to about 13 times higher than that of sodium salicylate as a reference material.

DOI： 10.1023/A:1024621214914

New VUV phosphor, NaLnGeO4:Eu3+ (Ln = rare earth) Reviewed

Kenji Toda, Yu-Ichiro Imanari, Takashi Nonogawa, Kazuyoshi Uematsu, Mineo Sato

Chemistry Letters 32 ( 4 ) 346 - 347 2003.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemical Society of Japan

The synthesis and luminescence properties of Eu3+-doped ordered olivine-type NaLnGeO4 (Ln = rare earth) phosphors are reported. Under vacuum-UV (VUV) excitation, this phosphor showed intense red emission due to the 5D0-7F2 transition. The Na(Y0.3Gd0.65Eu0.05)GeO4 phosphor with optimum composition and synthetic condition under 147 nm excitation were higher than those of (Y0.95Eu0.05)2O3.

DOI： 10.1246/cl.2003.346

Synthesis of phosphor materials using natural ore "serpentine" Reviewed

Yu-Ichiro Imanari, Takashi Nonogawa, Jun-Ichi Miyoshi, Kenji Toda, Kazuyoshi Uematsu, Mineo Sato, Katsunori Kosuge, Yoshihiro Nishisu, Mikio Kobayashi

Journal of the Ceramic Society of Japan 111 ( 1290 ) 151 - 154 2003

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

Serpentine is a hydrated ultra-mafic rock, which is primarily composed of magnesium silicate minerals such as chrysotile and antigorite. Fibrous chrysotile is the most common type of asbestos. Since the rich mines supplied serpentine in Japan, application of natural ore "serpentine" as raw materials for ceramics has one of the potentially lowest cost ceramics production. In this study, long afterglow phosphor, Sr2MgSi2O7, has been successfully synthesized using natural ore serpentinite. Eu2+ and Dy3+ co-doped compounds show long-lasting phosphorescence. This demonstrates that the "serpentine" could be used in preparing alkaline earth silicate phosphors.

DOI： 10.2109/jcersj.111.151

層状ペロブスカイトの光触媒特性 Reviewed

川上正人, 辻由浩, 清水研一, 上松和義, 戸田健司, 佐藤峰夫, 北山淑江

Journal of Ecotechnology Research 8 47 - 52 2002.12

Search for new vacuum-UV phosphors Reviewed

K. Toda, K. Uematsu, Y. Imanari, T. Nonogawa, M. Sato

Ceramic Engineering and Science Proceedings 23 861 - 868 2002.12

Room temperature synthesis and characterization of perovskite compounds Reviewed

K Toda, S Tokuoka, K Uematsu, M Sato

SOLID STATE IONICS 154 393 - 398 2002.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

A new soft chemical method has been developed to remove the rock-salt type layers in the Ruddlesden-Popper-type layered perovskite at room temperature. The rock-salt type (KF) blocks in the layered perovskite, K2NbO3F, were selectively dissolved into water to give three-dimensional perovskite, KNbO3, at room temperature. In the alkali metal aqueous solution, the ion-exchange reaction of parent layered compound with coexisting ions in the alkaline solution results in the new perovskites containing the other metal ions for the A-site. The development of this synthetic route could lead to interesting new metastable perovskite materials at low temperature. (C) 2002 Published by Elsevier Science B.V.

DOI： 10.1016/S0167-2738(02)00578-7

Preparation of iron phosphate cathode material of Li3Fe2(PO4)(3) by hydrothermal reaction and thermal decomposition processes Reviewed

M Sato, S Tajimi, H Okawa, K Uematsu, K Toda

SOLID STATE IONICS 152 247 - 251 2002.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Well-crystallized Li3Fe2(PO4)(3) with an orthorhombic beta-Fe-2(SO4)(3)-type structure was able to be synthesized by using two synthetic routes, where hydrothermal reaction and successive heat treatment with relatively low temperatures were employed. The samples prepared were found to show orthorhombic symmetry, contrary to the fact that a conventional solid state synthesis heating at temperatures higher than 1000 degreesC usually gives monoclinic symmetry. The sample showed two plateau potentials of 2.8 and 2.7 V vs. Li/Li+ upon discharge, and the total discharge capacity of the sample exhibited more than 80 mA h g(-1) under 0.5 mA cm(-2). (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0167-2738(02)00306-5

Synthesis and characterization of Perovskite-type ionic conductor: Li3yLa1-3y(Nb1-xWx)3O9 Reviewed

Y. Aoyama, A. Komeno, K. Toda, M. Sato

Key Engineering Materials 216 135 - 140 2002.12

New synthetic route of perovskite materials in the test tube Reviewed

K. Toda, K. Uematsu, N. Ohtake, S. Tokuoka, M. Sato

Ceramic Engineering and Science Proceedings 23 689 - 694 2002.12

Photocatalytic water splitting over spontaneously hydrated layered tantalate A2SrTa2O7·nH2O (A=H, K, Rb) Reviewed

Ken-Ichi Shimizu, Yoshihiro Tsuji, Masato Kawakami, Kenji Toda, Tatsuya Kodama, Mineo Sato, Yoshie Kitayama

Chemistry Letters ( 11 ) 1158 - 1159 2002.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemical Society of Japan

A series of layered perovskite-type tantalates with hydrated interlayer space, A2SrTa2O7·nH2O (A=H, K, Rb), exhibited efficient photocatalytic activity for water splitting into H2/O2 mixture under UV irradiation without loading metal co-catalysts.

DOI： 10.1246/cl.2002.1158

Characterization of potassium niobate produced by self-assembled nanosheet from aqueous solution Reviewed

K Toda, N Ohtake, M Kawakami, S Tokuoka, K Uematsu, M Sato

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 41 ( 11B ) 7021 - 7024 2002.11

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN SOC APPLIED PHYSICS

Submicron particles of potassium niobate KNbO3 were prepared by a colloid chemistry method. A rock-salt-type KF block in a layered perovskite, K2NbO3F, with a K2NiF4 type structure was selectively dissolved in water to produce perovskite nanosheets at room temperature. The self-assembly between perovskite nanosheets in a colloidal solution may enable shape control of potassium niobate powder. The microstructure, phase transition and mechanism of the solution process were investigated by transmission electron microscopy, X-ray diffraction and determination of ultraviolet-visible absorption spectra. [DOI: 10.1143/JJAP.41.7021].

DOI： 10.1143/JJAP.41.7021

Synthesis and characterization of new long persistent phosphor Reviewed

K Toda, Y Imanari, T Nonogawa, J Miyoshi, K Uematsu, M Sato

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 110 ( 4 ) 283 - 288 2002.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Rare earth-doped alkaline earth silicates, Sr2MgSi2O7:Eu2+, Dy3+ and Ca2MgSi2O7: Eu2+, Dy3+, with an akermanite-type structure show bright and long-lasting phosphorescence. After irradiation by a white-color fluorescent lamp (780 lm) for 5 min, the light blue emission of Sr2MgSi2O7: Eu2+, Dy3+ was observable by naked eye in the dark for over 100 min after removal of the excitation light source.

DOI： 10.2109/jcersj.110.283

Crystal structure of trivalent ion conductive perovskite: Y-x(Ta3xW1-3x)O-3 Reviewed

K Toda, Y Aoyama, M Sato

ASIAN CERAMIC SCIENCE FOR ELECTRONICS II AND ELECTROCERAMICS IN JAPAN V, PROCEEDINGS 228-2 277 - 280 2002

Language：English Publishing type：Research paper (scientific journal) Publisher：TRANS TECH PUBLICATIONS LTD

Crystal structure of A-site deficient perovskites, Y-x(Ta3xW1-3x)O-3 was determined by the Rietveld refinement method for neutron diffraction pattern. The Rietveld refinement indicates that a disorder-type compound with x = 0.06 crystallizes the orthorhombic system with the space group Pnma (No. 62) and lattice parameters a = 0.5373(3), b = 0.7547(5) and c = 0.5297(3) nm. The crystal structure of disorder-phase is a GdFeO3 type orthorhombic structure with no evidence for long range ordering of the vacancies in the partially occupied A-site.

New Synthetic Route of Perovskite Material in the Test Tube Reviewed

K. Toda, S. Tokuoka, K. Uematsu, M. Sato

Key Engineering Materials 214-215 67 - 72 2001.12

Crystal Structure of Fe16N2 Reviewed

K. Toda, M. Honda, Y. Orihara, M. Sato, F. Kanamaru

Key Engineering Materials 181-182 213 - 216 2000.12

Physical Properties of Non-Stoichiometric Rare Earth Orthoniobates Reviewed

K. Toda, M. Honda, Y. Ishimoto, M. Sato

Key Engineering Materials 181-182 217 - 220 2000.12

Single Crystal Growth of Lithium Ion Conductive Phosphates Reviewed

T. Suzuki, N. Hayakawa, K. Uematsu, K. Toda, M. Sato

Key Engineering Materials 181-182 183 - 186 2000.12

Trivalent Ionic Conductivity of Perovskite-Type Yx(Ta3xW1-3x)O3 Reviewed

N. Sakai, K. Toda, M. Sato

Electrochemistry 68 504 - 506 2000.12

Oxygen defect in non-stoichiometric europium orthoniobate, EuxNbO4-1.5(1-x) Reviewed

Kenji Toda, Masahito Honda, Yoko Ishimoto, Zuo-Guang Ye, Mineo Sato

Solid State Ionics 136-137 25 - 30 2000.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Science Publishers B.V.

The crystal chemistry of non-stoichiometric europium orthoniobate, EuxNbO4-1.5(1-x), prepared using Rb2CO3 flux, was studied. The lattice parameters vary clearly with the rare earth content of the orthoniobate specimens. In the Eu2O3-Nb2O5 system without a flux, the non-stoichiometric compound could not be synthesized as a single phase. With the use of flux, europium-deficient non-stoichiometric solid solution appears to form in which oxygen vacancies are the predominant defects. These non-stoichiometric compounds have the potential to act as new oxide ion conductors.

DOI： 10.1016/S0167-2738(00)00384-2

Enhancement of discharge capacity of Li3V2(PO4)3 by stabilizing the orthorhombic phase at room temperature Reviewed

Mineo Sato, Hirokazu Ohkawa, Kenji Yoshida, Mai Saito, Kazuyoshi Uematsu, Kenji Toda

Solid State Ionics 135 ( 1-4 ) 137 - 142 2000.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Science Publishers B.V.

Li3V2(PO4)3 and solid solutions of Li3-2x(V1-xZrx)2(PO4)3 were prepared by a solid state reaction. A high temperature orthorhombic phase of Li3V2(PO4)3 with a β-Fe2(SO4)3-type was successfully stabilized at room temperature by substituting Zr for V with substitution ratios beyond x = 0.05. The pure material of Li3V2(PO4)3 exhibited a cathode performance with two well defined regions of plateau at around 3.7 and 4.1 V vs. Li/Li+ upon charging and 3.6 and 4.0 V vs. Li/Li+ upon discharging, respectively, suggesting two types of phases produced upon the charge/discharge process. On the other hand, the cathode performance of the orthorhombic stabilized materials showed almost the same charge/discharge voltages as those of the pure material, but, with two plateaus slightly sloping, showed a considerably improved charge/discharge cycle performance compared to that of the pure material. Such improvement on the charge/discharge cycle performance is suggested to come from the disordered lithium ion arrangement in the orthorhombic phase.

DOI： 10.1016/S0167-2738(00)00292-7

Synthesis and characterization of ionic conductors; Li12/7+x(Li4/7Ti24/7-xMx)O-8 (M=Al, Cr and Fe) and Li12/7+2x(Li4/7Ti24/7-2xMg2x)O-8 with tunnel structure Reviewed

N Sakai, K Toda, M Sato, F Kanamaru

ELECTROCERAMICS IN JAPAN III 181-1 167 - 170 2000

New layered perovskite compound synthesized by the soft chemistry: KCa2Ta3O10 Reviewed

K. Toda, S. Takakuwa, N. Sakai, T. Teranishi, M. Sato

Key Engineering Materials 169-170 231 - 234 1999.12

The ionic conductivity of new ionic conductor Li3(In1-xScx)2(PO4)3 Reviewed

T. Suzuki, K. Yoshikawa, N. Hayakawa, K. Uematsu, K. Toda, M. Sato

Key Engineering Materials 169-170 205 - 208 1999.12

Preparation and ionic substitution of Dion-Jacobson type compounds CsLa(M,Mn) nO3n+1 (M = Nb, n = 2, 3) Reviewed

S. Takakuwa, T. Saitoh, K. Toda, F. Kanamaru

Key Engineering Materials 169-170 243 - 246 1999.12

Structure and property of layered perovskite type compounds (La,Sr)n+1FenO3n+1 and intercalation of LaSr3Fe3O10-delta Reviewed

T. Nishi, K. Toda, F. Kanamaru, T. Sakai

Key Engineering Materials 169-170 235 - 238 1999.12

Structural chemistry of new ion-exchangeable tantalates with layered perovskite structure: New Dion-Jacobson phase MCa2Ta3O10 (M = alkali metal) and Ruddlesden-Popper phase Na2Ca2Ta3O10 Reviewed

K. Toda, T. Teranishi, Z-G. Ye, M. Sato

Materials Research Bulletin 34 971 - 982 1999.12

Synthesis of Ruddlesden-Popper type (La,Sr)n+1VnO3n+1 (n = 1, 2, 3) Reviewed

M. Suzuki, F. Kanamaru, K. Toda, T. Sakai

Key Engineering Materials 169-170 239 - 242 1999.12

Improvement of discharge capacity of β-Fe2(SO4)3-type Li3V2(PO4)3 by stabilizing high temperature orthorhombic phase at room temperature Reviewed

Hirokazu Ohkawa, Kenji Yoshida, Mai Saito, Kazuyoshi Uematsu, Kenji Toda, Mineo Sato

Chemistry Letters ( 10 ) 1017 - 1018 1999

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemical Society of Japan

The cathode performance of a lithium ion battery was investigated for β-Fe2(SO4)3-type Li3V2(PO4)3 and Li3(V1 xZrx)2(PO4)3 (x=0.05, 0.1, 0.15, 0.2). On TG-DTA measurements, Li3V2(PO4)3 exhibited two types of phase transition, while Li3(V1-xZrx)2(PO4)3 exhibited no phase transition. Powder X-ray diffraction analysis and conductivity measurements confirmed an evidence for the stabilization of the high temperature phase at room temperature. The discharge capacity of the Zr-substituted Li3(V1-xZrx)2(PO4)3 samples became much larger than that of the pure Li3V2(PO4)3 sample.

DOI： 10.1246/cl.1999.1017

Single crystal growth and domain structure of CsLaTa2O7 Reviewed

S Tobitsuka, T Honma, T Wakayama, K Toda, M Sato

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 19 ( 6-7 ) 1559 - 1562 1999

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

A new layered perovskite compound of CsLaTa2O7 was synthesized and grown in the forms of powder and single crystal by a conventional solid state reaction and a flux method, respectively. The Rietveld analysis based on the powder sample showed a tetragonal system, while the observation of the as-grown single crystal by a polarized light microscope showed an orthorhombic system. The orthorhombic as-grown single crystal transformed to a tetragonal phase on annealing at a high temperature. (C) 1999 Elsevier Science Limited. All rights reserved.

DOI： 10.1016/S0955-2219(98)00476-2

Synthesis and lithium ionic conductivity of Li3-2x(In1-xZrx)(2)(PO4)(3) (0 <= x <= 0.20) Reviewed

K Yoshikawa, N Hayakawa, T Suzuki, K Uematsu, K Toda, M Sato

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 19 ( 6-7 ) 879 - 882 1999

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Lithium ion conductors, Li3-2x(In1-xZrx)(2)(PO4)(3) (0 less than or equal to x less than or equal to 0.20), were synthesized by a solid state reaction. A superionic conductive phase of Li3In2(PO4)(3) was stabilized down to room temperature, assisted by the substitution of Zr4+ for In3+ sites of Li3In2(PO4)(3). TG-DTA analysis indicated no phase transition in the samples with x superior to 0.05. The substituted samples showed much higher ionic conductivity by a couple of magnitude than that of Li3In2(PO4)(3). In particular, the highest conductivity at room temperature was 1.42 x 10(-5) Scm(-1) for Li-2.8(In0.9Zr0.1)(2)(PO4)(3). Thin films with the composition of Li-2.8(In0.9Zr0.1)(2) (PO4)(3) was prepared by a sol-gel method. A coating solution was made from lithium isopropoxide, indium isopropoxide, zirconium isopropoxide and diphosphorus pentaoxide. Well crystallized films were obtained on silicon dioxide and quartz glass substrates by dropping the coating solution, followed by firing over 873 K. In the temperatures above 473 K the lithium ionic conductivity of the film was slightly higher than that of sintered samples prepared by the solid state reaction at 1373 K. (C) 1999 Elsevier Science Limited. All rights reserved.

DOI： 10.1016/S0955-2219(98)00336-7

Synthesis and structure determination of reduced tantalates, Li2LaTa2O7, Li2Ca2Ta3O10 and Na2Ca2Ta3O10, with a layered perovskite structure Reviewed

Kenji Toda, Masaki Takahashi, Takashi Teranishi, Zuo-Guang Ye, Mineo Sato, Yukio Hinatsu

Journal of Materials Chemistry 9 ( 3 ) 799 - 803 1999

Language：English Publishing type：Research paper (scientific journal)

New reduced tantalates, Li2LaTa2O7, Li2Ca2Ta3O10 and Na2Ca2Ta3O10, with a layered perovskite structure have been synthesized by a chemical or an electrochemical intercalation reaction of the alkali metal cations with the parent Dion-Jacobson series compounds. The crystal structures of these compounds were determined by Rietveld analysis of powder X-ray diffraction patterns, and found to be analogous to those of the parent compounds. The intercalation of the lithium ion leads to a large contraction along the stacking direction of perovskite layers because of a higher interlayer charge density. These intercalation compounds are the first example of reduced tantalates with a layered perovskite structure.

DOI： 10.1039/a807038e

Possibility of superconductivity in new reduced tantalate and titanate with the layered perovskite structure Reviewed

K Toda, T Teranishi, M Sato

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 19 ( 6-7 ) 1525 - 1529 1999

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

New reduced tantalate, Na2Ca2Ta3O10, and titanate, Na1.0Ca0.95La2Ti3O10, were synthesized by intercalation reaction from the parent Dion-Jacobson and Ruddlesden-Popper type layered perovskite compounds. The crystal structure of the tantalate was determined by the Rietveld analysis of the powder X-ray diffraction pattern. The intercalation compound, Na2Ca2Ta3O10, is the first example of reduced tantalate with the Ruddlesden-Popper type structure. In some of reduced tantalate and titanate compounds, the diamagnetic signals have been observed below 7 K. Therefore, these compounds are thought to be good candidates for new oxide superconductors. (C) 1999 Elsevier Science Limited All rights reserved.

DOI： 10.1016/S0955-2219(98)00472-5

Structure refinement of lithium ion conductors Li3Sc2(PO4)(3) and Li3-2x(Sc1-xMx)(2)(PO4)(3) (M = Ti, Zr) with x = 0.10 by neutron diffraction Reviewed

T Suzuki, K Yoshida, K Uematsu, T Kodama, K Toda, ZG Ye, M Ohashi, M Sato

SOLID STATE IONICS 113 89 - 96 1998.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

The crystal structure of lithium ion conductors, Li3Sc2(PO4)(3) and Li3-2x(Sc1-xMx)(2)(PO4)(3) (M = Ti, Zr) with x = 0.10, were refined by Rietveld analysis for neutron diffraction patterns in order to confirm the site location and site occupancy for Li ions. The Rietveld refinement confirmed that a high disorder was introduced to three kinds of Li sites in the high temperature superionic conduction phase of Li3Sc2(PO4)(3). The high temperature phase was stabilized at room temperature by substituting Ti4+ or Zr4+ for Sc3+ sites. The stabilized materials were also found to have similar high disorder over the Li sites. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0167-2738(98)00279-3

Lithium intercalation and cathode performance of Li2CrTi (PO4)(3) Reviewed

M Sato, S Hasegawa, K Yoshida, K Toda

DENKI KAGAKU 66 ( 12 ) 1236 - 1240 1998.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELECTROCHEMICAL SOC JAPAN

Chemical and electrochemical lithium intercalation behavior was investigated on Li2CrTi(PO4)(3). Lithium ions with an almost one mole per formula were inserted by the chemical intercalation by n-butyllithium. The structure refinement was done by the Rietveld method for both parent and intercalated materials. The results showed that both materials crystallized in a lower crystal symmetry, R (3) over bar or C2/c, which is different from that previously reported in the literature. The intercalated material exhibited a cathode performance with a plateau at around 2.8 V vs. Li/Li+ upon charging and 2.4 V vs. Li/Li+ upon discharging.

Structural chemistry of new ion-exchangeable tantalates with layered perovskite structure: New reduced Ruddlesden-Popper phase, Na2Ca2Ta3O10 Reviewed

K Toda, T Teranishi, M Takahashi, ZG Ye, M Sato

SOLID STATE IONICS 113 501 - 508 1998.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

A new reduced tantalate, Na2Ca2Ta3O10, with layered perovskite structure was synthesized by an intercalation reaction from the parent sodium compound, NaCa2Ta3O10, The crystal structures of these compounds were determined by the Rietveld analysis of powder X-ray diffraction pattern. Although the framework of the perovskite layer of intercalation compound is analogous to that of the parent compound, the coordination of interlayer sodium ion in the intercalation compound is clearly distinct from that of the parent compound. The sodium ions within the interlayer of intercalation compound have a rock-salt coordination because of a too strong repulsive force fas a tetrahedral coordination. The intercalation compound, Na2Ca2Ta3O10, is the first example of a reduced! tantalate with a Ruddlesden-Popper type structure. (C) 1998 Published by Elsevier Science BN. All rights reserved.

DOI： 10.1016/S0167-2738(98)00316-6

Cathode Characteristics of Lithium Transition Metal Phosphate Synthesized by Ion-exchange Reaction Reviewed

K. Yoshida, K. Toda, K. Uematsu, M. Sato

Key Engineering Materials 157-158 289 - 296 1998.12

Chemical and electrochemical intercalation of lithium into the tantalates with the layered perovskite structure Reviewed

K Toda, M Takahashi, T Teranishi, K Uematsu, M Sato

DENKI KAGAKU 66 ( 12 ) 1241 - 1247 1998.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELECTROCHEMICAL SOC JAPAN

New reduced tantalates, Li2LaTa2O7 and Li2Ca2Ta3O10, with layered perovskite structure were synthesized by electrochemical or chemical intercalation reaction of lithium from the parent Dion-Jacobson series compounds. The crystal structures of these compounds were determined by the Rietveld analysis of powder X-ray diffraction pattern. The crystal structures of intercalation compounds were analogous to those of the parent compounds. The intercalation of the lithium ion leads to a large contraction along the stacking direction of perovskite layers because of a higher interlayer charge density. These intercalation compounds are the first example of reduced tantalates with layered perovskite structure.

Synthesis, Structure and Properties of the Magnetic Relaxor Ferroelectric Pb(Fe2/3W1/3)O3 [PFW] Reviewed

Z-G. Ye, K. Toda, M. Sato, E. Kita, H. Schmid

Journal of Korean Physical Society 32 1028 - 1031 1998.12

Concentration quenching of the Eu3+-activated luminescence in some layered perovskites with two-dimensional arrangement Reviewed

Toshihiko Honma, Kenji Toda, Zuo-Guang Ye, Mineo Sato

Journal of Physics and Chemistry of Solids 59 ( 8 ) 1187 - 1193 1998

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Ltd

The quenching of Eu3+-emission in the layered perovskite compounds SrRE2Al2O7, BaRE2Ti3O10, RETa3O9 and RbRETa2O7 (RE = rare earths) with two-dimensional arrangement of rare earth ions was investigated. The highest luminescence intensity was observed in both tantalum compounds, RETa3O9 and RbRETa2O7. The concentration quenching found in these compounds can be explained by a percolation model with two-dimensional interactions between the Eu3+ sites in the host lattice. The energy transfer between the Eu3+ ions takes place by the multipole-multipole interaction among the nearest-neighbor sites in the rare earth sublattice. © 1998 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0022-3697(98)00056-0

Stabilization of superionic conduction phase in Li3Sc2(PO4)(3) Reviewed

T Suzuki, K Yoshida, K Uematsu, T Kodama, K Toda, ZG Ye, M Sato

SOLID STATE IONICS 104 ( 1-2 ) 27 - 33 1997.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Lithium superion conductors, Li3+2x(Sc1-xMgx)(2)(PO4)(3), Li3-2x(Sc1-xMx)(2)(PO4)(3) (M=Ti, Zr, Sn, Hf) and Li3-4x(Sc1-xMx)(2)(PO4)(3) (M = Nb, Ta) were prepared by a solid-state reaction. TG-DTA analysis indicated no phase transition in Li3+2x(Sc1-xMgx)(2)(PO4)(3) and Li3-2x(Sc1-xMx)(2)(PO4)(2) (M = Ti, Zr, Sn, Kf) with x higher than 0.05, and in Li3-4x(Sc1-xMx)(2)(PO4)(3) (M=Nb, Ta) with x higher than 0.025. The room temperature ionic conductivity of Li3Sc2(PO4)(3) has been increased by three orders of magnitude with the highest conductivity observed in Li3-2x(Sc1-xTix)(2)(PO4)(3) with x = 0.20 and in Li3-2x(Sc1-xZrx)(2)(PO4)(3) with x = 0.10. It was ascribed to the stabilization of the high temperature superionic conduction phase and the introduction of vacancies on the Li+ sites by substituting Ti4+ Or Zr4+ for Sc3+.

DOI： 10.1016/S0167-2738(97)00404-9

Structure determination of new layered perovskite compound, NaLaTa2O7, synthesized by ion-exchange reaction Reviewed

K Toda, K Uematsu, M Sato

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 105 ( 6 ) 482 - 485 1997.6

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

A new layered perovskite compound, NaLaTa2O7, was synthesized by ion-exchange reaction of the rubidium compound, RbLaTa2O7. The crystal structure of the compound was determined by the Rietveld analysis for powder X-ray diffraction pattern. The crystal structure is analogous to that of the corresponding niobate compound, NaLaNb2O7. This layered perovskite compound is a new member of the Dion-Jacobson series with n=2 for the general formula M[A(n-1)B(n)O(3n+1)] (M=alkali metals).

DOI： 10.2109/jcersj.105.482

Synthesis and properties of lithium ion conductors Li3-2x(Sc1-xZrx)2(PO4)3 Reviewed

Mineo Sato, Takahito Suzuki, Kenji Yoshida, Kazuyoshi Uematsu, Kenji Toda, Zuo Guang Ye

Journal of Alloys and Compounds 250 ( 1 ) 510 - 514 1997

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Science S.A.

Lithium ion conductors, Li3-2x(Sc1-xZrx)2(PO4) (0qqxqq0.3), were prepared by a solid-state reaction. TG-DTA analysis indicated no phase transition in the samples with x superior to 0.05. X-ray powder diffraction analysis of these samples clearly showed the stabilization of a superionic conduction phase at room temperature with an orthorhombic system Pbcn. The highest conductivity was observed for the sample with x = 0.05, and ascribed to the stabilization of the superionic conduction phase and the introduction of vacancies on the Li+ sites by substituting Zr4+ for Sc3+.

DOI： 10.1016/S0925-8388(96)02746-6

Unusual concentration quenching of europium luminescence in new layered perovskite compound, RbLa1-xEuxTa2O7 (0 ≤ x ≤ 1) Reviewed

Kenji Toda, Toshihiko Honma, Mineo Sato

Journal of Luminescence 71 ( 1 ) 71 - 75 1997

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier

Dependence of emission intensity on Eu3+ concentration in new layered perovskite compound, RbLa1-xEuxTa2O7, with a perfect two-dimensional arrangement of luminescence center was studied. Critical value for concentration quenching is x = 0.5 for RbLa1-xEuxTa2O7. The critical concentration of this compound is discussed in terms of the crystal structure determined by the powder X-ray diffraction pattern using the Rietveld method. The concentration quenching found in this compound can be explained by means of a percolation model with two-dimensional interactions between Eu3+ sites in the host lattice.

DOI： 10.1016/S0022-2313(96)00097-X

Synthesis and structure determination of new layered perovskite compound, KLaTa2O7 Reviewed

Kenji Toda, Toshihiko Honma, Zuo Guang Ye, Mineo Sato

Journal of Alloys and Compounds 249 ( 1 ) 256 - 259 1997

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Science S.A.

A new layered perovskite compound, KLaTa2O7, was synthesized by ion-exchange reaction from the rubidium compound. RbLaTa2O7. The crystal structure of KLaTa2O7 was determined by Rietveld analysis from powder X-ray diffraction patterns. It is analogous to the structure of the corresponding niobate compound. This layered perovskite compound is a new member of the Dion-Jacobson series with n = 2 for the general formula A[Mn-1BnO3n+1] (A = monovalent cations, B = Nb or Ta). The structural features of KLaTa2O7 are discussed by comparison with other compounds of the ALaTa2O7 family and the titanate compounds.

DOI： 10.1016/S0925-8388(96)02752-1

Preparation of high lithium ion conducting LiLnSiO(4) (Ln=La,Sm) thin films by sol-gel method Reviewed

M Sato, H Ueda, Y Ohara, K Uematsu, K Toda

CHEMISTRY LETTERS ( 7 ) 657 - 658 1997

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

A soi-gel method was applied to prepare thin films of LiLnSiO(4) (Ln=La,Sm). The coating solution was made from lithium isopropoxide, silicon tetraethoxide, and tris(acetylacetonato)rare-earth. Well crystalline films with 0.1 similar to 0.3 mu m in thickness were obtained on alumina and quartz glass substrates by spin-coating, followed by firing over 400 degrees C. The lithium ionic conductivity of the films was much greater than that of sintered samples prepared by a conventional solid state reaction at 1000 degrees C.

DOI： 10.1246/cl.1997.657

Synthesis and Ionic conductivity of New Layered Perovskite Compound, Ag2La2Ti3O10 Reviewed

K. Toda, J. Watanabe, M. Sato

Solid State Ionics 90 15 - 19 1996.12

Synthesis and high ionic conductivity of new layered perovskite compounds, AgLaTa2O7 and AgCa2Ta3O10 Reviewed

K Toda, T Suzuki, M Sato

SOLID STATE IONICS 93 ( 1-2 ) 177 - 181 1996.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

New layered perovskite compounds, AgLaTa2O7 and AgCa2Ta3O10, have been synthesized by an ion-exchange reaction from parent compounds, RbLaTa2O7 and RbCa2Ta3O10. The crystal structures of silver ion-exchanged compounds were determined by the Rietveld analysis for powder XRD patterns. These compounds, which are probably metastable, could only be obtained by the ion-exchange reaction. The relatively high ionic conductivities attributed to the interlayer silver ions were observed at high temperatures.

DOI： 10.1016/S0167-2738(96)00518-8

Bulk and grain boundary ionic conduction in lithium rare earth silicates "LiLnSiO4" (Ln = La, Nd, Sm, Eu, Gd, Dy) Reviewed

M. Sato, Y. Kono, H. Ueda, K. Uematsu, K. Toda

Solid State Ionics 83 249 - 256 1996.12

Crystal structure determination and ionic conductivity of layered perovskite compounds NaLnTiO4 (Ln = rare earth) Reviewed

Kenji Toda, Yutaka Kameo, Satoru Kurita, Mineo Sato

Journal of Alloys and Compounds 234 ( 1 ) 19 - 25 1996.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier BV

The layered perovskite compounds NaLnTiO4 (Ln = La, Pr, Nd, Sm, Eu, Gd, Y and Lu) were synthesized by the solid state reaction. The crystal structure of these compounds were determined by the Rietveld analysis. Single phases of the compounds (except for Ln = Lu) could be prepared only under very restricted preparation conditions. The composition of NaLuTiO4 was not a single phase under the conditions employed in this study. Compounds NaLnTiO4 have a tetragonal symmetry for Ln = La-Nd, while an orthorhombic symmetry is observed for Ln = Sm-Lu. The stabilization of NaLnTiO4 is discussed on the basis of the relative sizes of the rare earth and the alkali metal ions. The lowering of the symmetry is considered to be introduced by the mismatch between TiO2 and LnO2 layers. Ionic conductivities attributed to the interlayer sodium ions were observed at high temperatures. The magnitude of ionic conductivity of NaLaTiO4, with a single perovskite layer, was much higher than that of Na2La2Ti3O10, with a triple perovskite layer. This high ionic conductivity is due to the weak interaction between the perovskite layer and interlayer sodium ions.

DOI： 10.1016/0925-8388(95)01969-3

New layered perovskite compounds, LiLaTiO4 and LiEuTiO4 Reviewed

K Toda, S Kurita, M Sato

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 104 ( 2 ) 140 - 142 1996.2

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

New layered perovskite compounds, LiLnTiO(4) (Ln=La and Eu), have been synthesized by an ion-exchange reaction from parent sodium compounds, NaLnTiO(4). The crystal structures of LiLaTiO4 and LiEuTiO4 were determined by Rietveld analysis of the powder X-ray diffraction (XRD) patterns. The lithium ion-exchanged compounds retain the crystal symmetry of the parent phases. Although the framework of the perovskite layer of these compounds is the same as that of the parent compounds, there exists a fundamental difference. The lithium ions within the interlayer have a tetrahedral coordination because of small ionic radius for a rock-salt coordination. The structure of LiLaTiO4 and LiEuTiO4 consist of intergrowths of the perovskite sheets with the layers of Li-O in a tetrahedral coordination and those of Ln-O in a distorted rock-salt coordination. These compounds exhibit new phases analogous to the Ruddlesden-Popper phase.

DOI： 10.2109/jcersj.104.140

Intercalation of water in a layered perovskite compound, NaEuTiO4 Reviewed

Kenji Toda, Yutaka Kameo, Satoru Kurita, Mineo Sato

Bulletin of the Chemical Society of Japan 69 ( 2 ) 349 - 352 1996

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemical Society of Japan

Intercalation of water was observed in a layered perovskite compound, NaEuTiO4, leading to its hydrated derivatives. There are some metastable intermediates in the hydrated derivatives. The hydration process includes several steps that are topotactic. The crystal structure of the hydrated derivatives was identified by Rietveld analysis for the powder X-ray diffraction pattern. It is confirmed that the water molecules are inserted into the sodium layer of NaEuTiO4.

DOI： 10.1246/bcsj.69.349

Synthesis and structure determination of new layered perovskite compounds, ALaTa2O7 and ACa2Ta3O10 (A = Rb, Li) Reviewed

Kenji Toda, Mineo Sato

Journal of Materials Chemistry 6 ( 6 ) 1067 - 1071 1996

Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry

New layered perovskite compounds of RbLaTa2O7 and RbCa2Ta3O10, whose Rb+ ions can be ion-exchanged have been synthesized directly by a solid-state reaction. Lithium ion-exchanged compounds, LiLaTa2O7 and LiCa2Ta3O10, have also been synthesized by ion-exchange reactions of the rubidium compounds with LiNO3 molten salt. The crystal structures of these compounds have been determined by Rietveld analysis of their powder X-ray diffraction patterns. The crystal structures of these compounds are analogous to those of the corresponding niobate compounds. These compounds are new members of the Diori-Jacobson series with the general formula A[Mn-1BnO3n+i] (A = alkali metal), with n = 2 and 3.

DOI： 10.1039/jm9960601067

Crystal structure determination of ion-exchangeable layered perovskite compounds, K2La2Ti3O10 and Li2La2Ti3O10 Reviewed

Kenji Toda, Jun Watanabe, Mineo Sato

Materials Research Bulletin 31 ( 11 ) 1427 - 1435 1996

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Ltd

The crystal structure of the ion-exchangeable layered perovskite compounds K2La2Ti3O10 and Li2La2Ti3O10 were determined by Rietveld analysis for the powder X-ray diffraction pattern. Although the framework of the perovskite layer of lithium compound is the same as those of the corresponding sodium and potassium compounds, a fundamental difference exists. The lithium ions within the interlayer have a tetrahedral coordination because the ionic radius is too small for a rock-salt coordination. The layered perovskite compound Li2La2Ti3O10 exhibits a new phase analogous to the Ruddlesden-Popper phase.

DOI： 10.1016/0025-5408(96)00135-3

Synthesis and ionic conductivity of novel layered perovskite compounds, AgLaTiO4 and AgEuTiO4 Reviewed

Kenji Toda, Satoru Kurita, Mineo Sato

Solid State Ionics 81 ( 3-4 ) 267 - 271 1995.11

Language：English Publishing type：Research paper (scientific journal)

Novel compounds, AgLaTiO4 and AgEuTiO4, have been synthesized by an ion-exchange reaction from parent compounds, NaLaTiO4 and NaEuTiO4. The crystal structure of the silver ion-exchanged compounds was determined by the Rietveld analysis for powder XRD patterns. The silver ion-exchange compounds retain the structural characteristics of the parent phases. The interlayer silver ions in the silver ion-exchanged compounds have a rock-salt type coordination. These compounds, which are probably metastable, could only be obtained by the ion-exchange reaction. The ionic conductivities attributed to the interlayer silver ions were observed at high temperatures. The ionic conductivity of AgLaTiO4 was much higher than that of NaLaTiO4. Such a high ionic conductivity is probably due to the higher polarizability of silver ion. © 1995.

DOI： 10.1016/0167-2738(95)00184-8

Luminescence properties of layered perovskites activated by Eu3+ ions Reviewed

Kenji Toda, Yutaka Kameo, Masatoshi Ohta, Mineo Sato

Journal of Alloys and Compounds 218 ( 2 ) 228 - 232 1995.3

Language：English Publishing type：Research paper (scientific journal)

Dependence of emission intensity on Eu3+ concentration in Na2Gd2(1-x)Eu2xTi3O10 with a triple perovskite layer and NaGd1-xEuxTiO4 with a single perovskite layer was studied. Critical values for concentration quenching are x = 0.40 for Na2Gd2(1-x)Eu2xTi3O10 and x = 0.25 for NaGd1-xEuxTiO4. The difference in the critical concentration between both compounds is discussed in terms of their crystal structures determined by the powder X-ray diffraction patterns using the Rietveld method. The concentration quenching found in these compounds can be explained by means of a percolation model with nearly two-dimensional interactions between Eu3+ sites in the host lattice. © 1995.

DOI： 10.1016/0925-8388(94)01395-0

Crystal structure and ionic conductivity of a layered perovskite, Na2La2Ti3O10 Reviewed

Kenji Toda, Yutaka Kameo, Masayuki Fujimoto, Mineo Sato

Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan 102 737 - 741 1994

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Soc of Japan

An ion-exchangeable layered perovskite compound, Na2La2Ti3O10, was directly synthesized by a solid-state reaction. The crystal structure of Na2La2Ti3O10 was determined by electron diffraction analysis and Rietveld analysis for the powder X-ray diffraction pattern. The unit cell is tetragonal with a = 0.383528(7) nm, c = 2.85737(7) nm and Z = 2 with the space group I4/mmm (No. 139). The structure of this compound is analogous to that of the Ruddlesden-Popper phases. The ionic conductivity of Na2La2Ti3O10 was not very high compared with those of niobate compounds, NaLaNb2O7 and NaCa2NaNb4O13. Such a low ionic conductivity is due to the rigid rock-salt-type coordination around sodium ions located at the interlayer.

DOI： 10.2109/jcersj.102.737

層状ペロブスカイトK2La2Ti3O10およびその銀イオン交換体の構造とイオン伝導性 Reviewed

佐藤峰夫, 戸田健司, 渡辺潤, 上松和義

日本化学会誌 5 640 - 646 1993.12

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