| Project/Area Number |
07554032
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Inorganic chemistry
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| Research Institution | The University of Tokyo |
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Principal Investigator |
UEDA Yutaka The University of Tokyo Institution for Solid State Physics (ISSP), Professor, 物性研究所, 教授 (20127054)
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| Co-Investigator(Kenkyū-buntansha) |
TOJIMA Katsuyoshi MacScience Company, Managing Director, 熱分析事業部, 部長
HAYASHI Akihiko University of Tokyo, ISSP,Research Associate, 物性研究所, 助手 (10228562)
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| Project Period (FY) |
1995 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥12,200,000 (Direct Cost: ¥12,200,000)
Fiscal Year 1997: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1995: ¥11,100,000 (Direct Cost: ¥11,100,000)
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| Keywords | high pressure TG-DTA / high oxygen pressure / phase equilibrium / order-disorder transition / highly oxygenated state / high temperature / 酸素不定比性 / 熱平衡 / 熱分解 / 相転移 / 過剰酸素 / 金属イオン欠損 |
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| Research Abstract |
In this study, we have developed a new apparatus by which thermogravimetry and differential thermal analysis (TG-DTA) can be performed under high gaseous pressure. By using this apparatus, we have investigated oxygen nonstoichiometry and phase transition in high temperature superconductors RBa_2Cu_3O_y (R=Y,Sm, Er) under high oxygen pressure up to 150 atm. We observed a reversible weight change between room temperature and 300ﾟC above 10 atm. From various experiments it was concluded that this behavior is due to buoyancy under a dense gas. The behavior was quantitatively explained by the calculation taking buoyancy into a consideration. The observed TG curves were corrected by using this calculation. RBa_2Cu_3O_y shows a transition from orthorhombic to tetragonal which is a kind of order-disorder transition. It has been unknown how is the transition in the region of high oxygen content. We first observed the transition in such high oxygen content region. The transition temperature (T_t) has a trend to saturate at 830ﾟC in YBa_2Cu_3O_y and 730ﾟC in SmBa_2Cu_3O_y around y=6.75, and in ErBa_2Cu_3O_y it tends to increase again above y=6.75. These behaviors suggest an existence of a new phase with an another arrangement of oxygen vacancies around y=6.75. And we found interesting pressure dependences of thermal decomposition in some oxalic acids. This machine is available for hydrogen atmosphere.
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