研究者詳細 - 吉野　正人

論文 - 吉野　正人

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Photoluminescence around 1.54 mu m from Er-containing ZnO at room temperature 査読有り

Zhou, Z; Komaki, T; Koizumi, A; Komori, T; Yoshino, M; Morinaga, M; Fujiwara, Y; Takeda, Y

Mater. Trans. 45 巻 ( 7 ) 頁： 2003-2007 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

The photoluminescence (PL) around the wavelength of 1.54 mum from the Er-containing ZnO specimens was measured at room temperature by the indirect excitation of the He-Cd laser (325 nm). The PL intensity varied greatly with the Er concentration and the specimen preparation conditions as well. The specimens with the Er content of about 2.6 at%, sintered at 1623 K, and cooled quickly to room temperature in air showed the highest PL intensity at 1.534 mum. The local structure of the optically active Er centers in ZnO was also discussed, and the appropriate optically active center might be the Er ions existing in the grain boundaries.

A universal relation between electron density minima and ionic radii in ceramics 査読有り

Yoshino, M; Morinaga, M; Shimode, A; Okabayashi, K; Nakamatsu, H; Sekine, R

Mater. Trans. 45 巻 ( 7 ) 頁： 1968-1972 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

A universal relation between electron density minima and ionic radii, was discovered from the first principles calculations of electronic structures in ceramics over 60 species, including oxides, borides, carbides, nitride and fluorides. Every ceramic falls on a curve Of log(rho(min)Z(-3)) vs. 2(Z/n)r(min), where rho(min) is the minimum electron density in the line linking the first-nearest-neighbor nuclei, r(min) is the distance r at rho(min) is the atomic number, and n is the principal quantum number.

Electrical conductivity of Cu-doped ZnO and its change with hydrogen implantation 査読有り

Zhou, Z; Kato, K; Komaki, T; Yoshino, M; Yukawa, H; Morinaga, M; Morita, K

J. Electroceram. 11 巻 ( 1-2 ) 頁： 73-79 2003年

記述言語：英語掲載種別：研究論文（学術雑誌）

The doping effects of Cu on the electrical conductivity of ZnO were studied in the simple binary system through the ac impedance spectroscopy. The Cu doping decreased the electrical conductivity of ZnO by several orders of magnitude. The Cu doping decreased the electrical conductivity of ZnO both in the grain and in the grain boundary. Hydrogen was introduced into the Cu-doped ZnO specimens by the ion implantation technique. The electrical conductivity of the hydrogen-implanted layer increased by about 9 orders of magnitude at most. The mechanism for such a hydrogen effect was also discussed.

電子密度分布に見られるユニバーサルな関係

吉野正人、岡林功介、下出晃広、森永正彦、中松博英、関根理香

DV-Xa研究協会会報 16 巻 ( 1 ) 頁： 46-48 2003年

Local geometries and energetics of hydrogen in acceptor-doped SrZrO3 査読有り

Yoshino, M; Liu, Y; Tatsumi, K; Tanaka, I; Morinaga, M; Adachi, H

Solid State Ion. 162 巻頁： 127-133 2003年

記述言語：英語掲載種別：研究論文（学術雑誌）

The local geometry and chemical bonding around proton and acceptor dopant in perovskite-type oxide SrZrO3 have been investigated by the pseudopotential method and the DV-Xalpha molecular orbital method. Special attention is directed towards the MO6 octahedron in the perovskite-type structure, where Ms are acceptor dopants (e.g., Y and Al) substituted for Zr ions in the oxide. <BR>It is shown that local electronic state of the constituent ions in the MO6 octahedron is a good measure of the local geometrical change of the octahedron with doping. For example, there is a strong resemblance in the local ionic state and hence the local geometry of the octahedron between the undoped and Y-doped oxides. However, there is little resemblance between the undoped and Al-doped oxides. The calculated activation energy for protonic conduction is higher in the Al-doped oxide than that in the Y-doped oxide, in agreement with experimental results. From these results, it is found that such an acceptor dopant that does not change local electronic state or local geometry of the octahedron is a preferable element for enhancing protonic conductivity in perovskite-type oxides.

Energetics of hydrogen states in SrZrO3 査読有り

Yoshino, M; Liu, Y; Tatsumi, K; Tanaka, I; Morinaga, M; Adachi, H

Mater. Trans. 43 巻 ( 7 ) 頁： 1444-1450 2002年

記述言語：英語掲載種別：研究論文（学術雑誌）

The optimized geometries and formation energies of hydrogen in the perovskite-type oxide, SrZrO3, have been calculated using the density functional theory under the generalized gradient approximation (GGA). The stable hydrogen sites in the oxide are examined with special interests. It is shown that the hydrogen is tightly bound to an oxygen ion and located slightly outside the ZrO6 octahedron in SrZrO3. The O-H bond orientates towards the second-nearest-neighbor oxygen ion, which induces large local displacements of adjacent oxygen ions. For example, the nearest-neighbor oxygen ions tend to approach the hydrogen. The addition of an acceptor dopant, yttrium, modifies such local distortion of oxygen ions around the hydrogen as to increase protonic conductivity. In addition, the calculated hydrogen formation energy shows that the hydrogen behaves as a shallow donor in SrZrO3. The fundamental principles of doping and atmosphere control in proton conducting oxides are also given in view of energetics.

水素修飾されたペロブスカイト型酸化物の局在量子構造査読有り

吉野正人、劉軼、森永正彦

セラミックス 37 巻 ( 6 ) 頁： 457-462 2002年

化合物中の原子の周りの電子密度分布と化学結合

吉野正人、湯川宏、森永正彦

DV-Xa研究協会会報 15 巻 ( 1 ) 頁： 40-42 2002年

DV-Xα法による材料設計-水素と材料-

森永正彦、湯川宏、吉野正人

DV-Xa研究協会会報 15 巻 ( 1 ) 頁： 17-24 2002年

Local Electronic Structures and Chemical Bonding in Proton Conducting Perovskite-type Oxides 査読有り

Yoshino, M; Mutiara, E; Kato, K; Yukawa, H; Morinaga, M

Proceedings of Fourth Pacific Rim International Conference on Advanced Materials and Processing (PRICM4) 頁： 563-566 2001年

ペロブスカイト型酸化物SrZrO3中のアクセプタイオンの周りの局所電子状態とプロトン伝導性

吉野正人、加藤勝也、Etty Mutiara、湯川宏、森永正彦

DV-Xa研究協会会報 14 巻 ( 1 ) 頁： 70-73 2001年

Theoretical Study of Oxygen-vacancy Defects in Ferroelectric BaTiO3

14 巻 ( 1 ) 頁： 114-117 2001年

Local electronic structures around hydrogen and acceptor ions in perovskite-type oxide, SrZrO3 査読有り

Yoshino, M; Nakatsuka, K; Yukawa, H; Morinaga, M

Solid State Ion. 127 巻 ( 1-2 ) 頁： 109-123 2000年

記述言語：英語掲載種別：研究論文（学術雑誌）

Local electronic structures around hydrogen and acceptor ions in SrZrO3 are simulated by the DV-X alpha molecular orbital method. In pure SrZrO3, there is a band gap of about 6 eV between the O-2p valence band and the Zr-4d conduction band, in agreement with experiments. When Y or Sc is doped into SrZrO3, an acceptor level appears just above the valence band. When hydrogen is introduced into SrZrO3, a donor level appears below the conduction band. Also, an oxygen ion vacancy makes the defect level below the conduction band. It is shown that charge compensation takes place among these acceptor, donor and defect levels. In addition, local electronic structure around hydrogen is found to change largely with the acceptor dopants, Sc and Y. For example, the metal-oxygen bond strength changes in the order, Y-O < Zr-O < Sc-O, which probably modifies the thermal vibrational amplitude of oxygen ions near hydrogen, and affects protonic conductivity in the doped SrZrO3.

プロトン伝導性ペロブスカイト型酸化物BaZrO3の電子状態

吉野正人、加藤勝也、湯川宏、森永正彦

DV-Xa研究協会会報 13 巻 ( 1 ) 頁： 27-31 2000年

Roles of the hydride forming and non-forming elements in hydrogen storage alloys 査読有り

Nakatsuka, K; Yoshino, M; Yukawa, H; Morinaga, M

J. Alloy. Compd. 295 巻頁： 222-226 1999年

記述言語：英語掲載種別：研究論文（学術雑誌）

The electronic structures of small octahedral model clusters containing hydrogen, 3d, 4d, 5d transition and non-transition elements are investigated by the DV-X alpha molecular orbital method. It is found that hydrogen makes a strong chemical bond with the hydride non-forming elements, B, as long as the hydride forming elements, A, exist in the neighborhood. This is a reason why hydrogen is located preferentially near the hydride non-forming elements in many hydrides. Also it is suggested that the ratio of the A-B bond strength to the A-A bond strength lies in a certain range for conventional hydrogen storage A-B alloys. (C) 1999 Elsevier Science S.A. All rights reserved.

ペロブスカイト型酸化物SrRuO3の電子状態と構造相転移の機構

吉野正人、川口光晴、湯川宏、森永正彦

DV-Xa研究協会会報 12 巻 ( 1 ) 頁： 118-122 1999年

Modification of Electronic Structure Due to Phase Transition in Perovskite-type Oxide, SrZrO3 査読有り

Yoshino, M; Yukawa, H; Morinaga, M

Proceedings of an International Conference on Solid - Solid Phase Transformations (PTM'99) (Kyoto, May 1999) 頁： 645-648 1999年

Molecular Orbital Calculation of the Electronic Structures of Hydrogen in Perovskite-type Oxide, SrZrO3 査読有り

Yoshino, M; Nakatsuka, K; Yukawa, H; Morinaga, M

Reports of Korea-Japan DV-Xa Joint Symposium (Korea, August 1998) 11 巻 ( 1 ) 頁： 44-46 1998年

Electronic Structures of Polymorphous Phases in Perovskite-type Oxide, SrZrO3 査読有り

Yukawa, H; Yoshino, M; Morinaga, M

Reports of Korea-Japan DV-Xa Joint Symposium (Korea, August 1998) 11 巻 ( 1 ) 頁： 50-52 1998年

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