Faculty Profiles - TODA Kenji

Papers - TODA Kenji

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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+.

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