| Project/Area Number |
10450239
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
MIZUSAKI Junchiro TOHOKU UNIVERSITY, RESEARCH INSTITUTE FOR SCIENTIFIC MEASUREMENTS, PROFESSOR, 科学計測研究所, 教授 (90092345)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAMURA Kenichi TOKYO INSTITUTE OF TECHNOLOGY, GRADUATE SCHOOL OF SCIENCE AND ENGINEERING, ASSOCIATE PROFESSOR, 大学院・理工学研究科, 助教授 (50270830)
NIGARA Yutaka TOHOKU UNIVERSITY, RESEARCH INSTITUTE FOR SCIENTIFIC MEASUREMENTS, ASSOCIATE PROFESSOR, 科学計測研究所, 助教授 (90006148)
KAWADA Tatsuya TOHOKU UNIVERSITY, RESEARCH INSTITUTE FOR SCIENTIFIC MEASUREMENTS, ASSOCIATE PROFESSOR, 科学計測研究所, 助教授 (10271983)
YASHIRO Keiji TOHOKU UNIVERSITY, RESEARCH INSTITUTE FOR SCIENTIFIC MEASUREMENTS, RESERCH ASSOCIATE, 科学計測研究所, 助手 (20323107)
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| Project Period (FY) |
1998 – 2000
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥12,600,000 (Direct Cost: ¥12,600,000)
Fiscal Year 2000: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1999: ¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 1998: ¥8,900,000 (Direct Cost: ¥8,900,000)
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| Keywords | PEROVSKITE-TYPE OXIDE / SELF-DIFFUSION COEFFICIENT / CHEMICAL-DIFFUSION COEFFICIENT / THERMAL EXPANSION COEFFICIENT / SOLID OXIDE FUEL CELL / OXYGEN ELECTRODE / VACANCY DIFFUSION COEFFICIENT / OXYGEN NONSCTOICHIOMETRY / 化学拡散係数 / 固体酸化物燃料電池 / 酸素不定比性 / クロム酸ランタン / マンガン酸ランタン / 拡散 / 酸素過剰 / 金属不足 / ペロブスカイト型酸化物 / Bサイト / 空孔 |
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| Research Abstract |
In the perovskite-type oxides, ABO_3, oxygen vacancies are easily formed while metal vacancies are not. Particularly, B-site vacancy is considered hardly exists because they are closely linked each other via oxygen ions to form a rigid crystal structure. LaMnO_3-based perovskite-type oxides are known to display metal deficient nonstoichiometry under oxygen rich atmospheres. The defect structure related to this nonstoichiometry has been a big unsolved problem. Neutron and X-ray diffraction studies could not reveal the position of defects whether on A-site only or on both A- and B-site. Moreover, there is no clear experimental evidence whether the predominant defect is oxygen interstitial or metal vacancy. This project aims to clarify the nature of defects in the perovskite-type oxides with particular focus on the metal deficient nonstoichiometry of LaMnO_3.
Measurements were made on volume variation of dense LaMnO_3 with the variation of oxygen partial pressure between 0.0001 and 1 atm by a dilatometer. A sample of 15 mm in length expands with oxidation and contracts with reduction for 10 〜 20 μm in 10 days. A high temperature XRD analysis gives the change of lattice volume in the inverse direction. This result infers the predominant defect of metal deficient LaMnO_3 as metal vacancy.
Since the diffusion of ions proceeds via vacancy, the diffusivity of A- and B-site ions are measured to compare the defect concentration of both sites. As an example of oxygen deficient perovskite-type oxides, YCrO_3 was selected and impurity diffusion coefficient of La on A-site and Mn on B-site were measured. Unexpectedly, the diffusion coefficient of La and Mn was essentially the same, suggesting that the concentration of vacancy on A- and B-site are the same. As to the metal deficient LaMnO_3, impurity difusion on B-site was found smaller than that on A-site by several orders of magnitude. In the metal deficient LaMnO_3, vacancies are predominantly formed on A-site.
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