1997 Fiscal Year Final Research Report Summary
Study on fast ion dynamics in superionic conductors
| Project/Area Number |
07239101
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Research Institution | Research Institute for Science Measurement, Tohoku University |
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Principal Investigator |
ISGIGAME Mareo Tohoku Univ., RISM, Professor, 科学計測研究所, 教授 (40006143)
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| Co-Investigator(Kenkyū-buntansha) |
OKAZAKI Hideo Niigata Univ., Faculty of Sciences, Professor, 理学部, 教授 (60018265)
SHIN Shik Univ. of Tokyo, ISSP, Associate Professor, 物性研究所, 助教授 (00162785)
KOTO Hichiro Tokushima Univ., Faculty of the Integrated Arts and Sciences, Professor, 総合科学部, 教授 (40029872)
KAWAZOE Yoshiyuki Tohoku Univ., IMR, Professor, 金属材料研究所, 教授 (30091672)
ISHII Tadao Okayama Univ. Faculty of Enginieering, Lecturer, 工学部, 講師 (90033240)
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| Project Period (FY) |
1995 – 1997
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| Keywords | proton conductor / perovskite-type oxides / superlattice / laser ablation / photoemission / EXAFS / molecular dynamics / ion dynamics |
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| Research Abstract |
In this study, proton conducting superlattice was fabricated and their fundamental characterization has been investigated (Ishigame) and the ion dynamics in perovskite-type proton conductors have been investigated experimentally from the view points of crystal structure (Koto) and electronic structure (Shin). Furthermore, fundamental theory on ion dynamics including electrons was investigated (Ishii) and molecular dynamics simulation in superlattice (Okazaki) and the ab initio molecular-dynamics of proton migration (Kawazoe) have been performed.
(Ishigame) SrCeィイD20.95ィエD2YbィイD20.05ィエD2OィイD23ィエD2-SrZrィイD20.95ィエD2YbィイD20.05ィエD2OィイD23ィエD2 superlattices were synthesized by laser ablation method and their fundamental characterization was performed by XRD, RBS, Raman scattering and optical absorption measurements. The electrical conductivity and FTIR-ATR studies showed that those superlattices has proton conductivity.
(Shin) Photoemission study of the electronic structure of p-type SrTiィイD2l-
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xィエD2ScィイD2xィエD2OィイD23ィエD2 suggests that the hybridization effect between the Ti 3d and O2p states becomes stronger than undoped SrTiOィイD23ィエD2. The dopant concentration dependence shows that the covalency is the strongest when the Sc concentration is 2 mol%. These facts suggest that the covalency related with the protonic conduction.
(Koto) SrZrィイD21-xィエD2YbィイD2xィエD2OィイD23ィエD2 was studied by XAFS and powder XRD to elucidate the crystal and local structures. The interatomic distances Zr-O and Yb-O decrease with increasing temperature though the lattice-constants increase with increasing temperature indicating a higher symmetry of the polyhedron around Zr and Yb ions at higher temperatures. The increase of oxide ion vacancies must play an important role in the promotion of the proton conductivity at high temperature.
(Okazaki) Molecular dynamics calculation has been applied to YSZ and CSZ superlattices and AgI-type ionic conductor. It was found that the oxygen ion diffusion takes place frequently in regions near Y or Ca rich layer. The results showed that collaborative motion between two ions plays an important role for ion dynamics in AgI-type ionic conductor.
(Ishii) It was found that the mechanism of "universal law" in the dynamic conductivity on regular and randam superlattices originates in the structure of inherent relaxation mode miniband and that the coupling of disorder of mobile ions and lattice distortion indaces the 1st-order phase transition, such that the larger the coupling is, material becomes more unstable.
(Kawazoe) Proton absorption and diffusion in SrTiOィイD23ィエD2 with and without oxygen vacancies have been studied by the ab initio molecular-dynamics within local density functional theory using ultrasoft pseucbpotentials. In the SrTiOィイD23ィエD2 with oxygen vacancy, proton tends to move to the vacancy position. Less
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