Faculty Profiles - TODA Kenji

Papers - TODA Kenji

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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.

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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

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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

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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

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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

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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

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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

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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

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