2004 Fiscal Year Final Research Report Summary
Accurate Crystal Structural Study on the Materials Science of Perovskite-Type Crystal by Synchrotron Radiation Powder Diffraction
| Project/Area Number |
14540303
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅰ(光物性・半導体・誘電体)
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| Research Institution | OKAYAMA UNIVERSITY |
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Principal Investigator |
KUROIWA Yoshihiro Okayama University, Faculty of Science, Associate Professor, 理学部, 助教授 (40225280)
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| Co-Investigator(Kenkyū-buntansha) |
SAWADA Akikatsu Okayama University, Faculty of Science, Professor, 理学部, 教授 (30023154)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Synchrotron Radiation / Powder X-ray Diffraction / Perovskite / Ferroelectric Compound / Structure Analysis / Charge Density |
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| Research Abstract |
The ferroelectric behavior of perovskite oxides with the chemical formula ABO_3 is strongly influenced by replacing A and/or B atoms with the other atoms. Many functional perovskite oxides have been discovered taking advantage of this replacement effect. However, for the microscopic origin of the ferroelectricity, incomplete interpretation was presented why crystallographically similar, but chemically different, such perovskite oxides exhibit very different ferroelectric behavior. From the 1990s, theoretical studies based on the first-principles calculations have been making great advances to understand the ferroelectric instability of perovskite oxides. We have been also making advances in experimental studies obtaining the accurate crystal structure by X-ray diffraction.
In this project, electron charge density distributions of perovskite oxides and related materials have been widely investigated associated with the phase transitions, by analyzing high-energy synchrotron-radiation powder diffraction data by the maximum entropy method(MEM)/Rietveld method. Two distinctive structural features, that is, significant lower covalent bonding electron density on the B-O bond and anisotropic charge density distributions around O atom, are observed in antiferroelectric oxides in the cubic phase. These features can be a clue to understanding why a certain perovskite oxide shows antiferroelectric phase transition.
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