Faculty Profiles - TODA Kenji

Papers - TODA Kenji

Division display 141 - 160 of about 225 ／ All the affair displays >>

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

Web of Science

researchmap

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

Web of Science

researchmap

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

Web of Science

researchmap

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

Web of Science

researchmap

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

Web of Science

researchmap

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.

Web of Science

researchmap

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

Scopus

researchmap

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

Web of Science

researchmap

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.

Web of Science

researchmap

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

Silica gels and porous glasses thermally treated at various temperatures were examined for use as an adsorbent to separate tritiated water (HTO) with an adsorption method. The HTO was adsorbed much stronger than H2O. A high partition coefficient of 1.38 was observed for the thermally treated silica gel at 1100°C in vacuo. From the measurement of IR 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.

DOI： 10.3769/radioisotopes.53.435

CiNii Article

researchmap

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

Web of Science

researchmap

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

Web of Science

researchmap

　 PREV - NEXT 　

<TODA Kenji>

Papers - TODA Kenji