The Study of Thermal Equilibrium and Highly Oxygenated State under High Oxygen Pressure

高氧压力下热平衡和高氧态的研究

• 批准号: 07554032
• 负责人: UEDA Yutaka
• 金额: $ 7.81万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07554032/
• 关键词: 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

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.

在本研究中，我们开发了一种新的装置，通过它可以在高气压下进行热重和差热分析（TG-DTA）。利用该装置，我们研究了高温超导体RBa_2Cu_3O_y（R=Y，Sm，Er）中氧的非化学计量比和相变。我们观察到在室温和300 ° C（高于10 atm）之间的可逆重量变化。从各种实验中可以得出结论，这种行为是由于在稠密气体下的浮力。通过考虑浮力的计算，定量地解释了这种行为。通过使用该计算校正了观察到的TG曲线。RBa_2Cu_3O_y表现出从正交相到四方相的有序-无序转变。在高氧含量的区域中是如何转变的一直是未知的。我们首次在高氧含量区观察到这种转变。YBa_2Cu_3O_y和SmBa_2Cu_3O_y在y=6.75附近的转变温度（T_t）分别在830 ℃和730 ℃达到饱和，而ErBa_2Cu_3O_y在y=6.75以上的转变温度（T_t）又趋于增加。这些行为表明，存在一个新的阶段与另一种安排的氧空位约y=6.75。我们发现了一些草酸的热分解与压力的关系。本机适用于氢气环境。

项目成果

Atsushi Goto: "Phase Diagram for the Spin Pseudogap in LaBa_2Cu_3O_y Studied by NMR." Physical Review B. 55. 12736-12741 (1997)

Atsushi Goto：“通过 NMR 研究 LaBa_2Cu_3O_y 中自旋赝能隙的相图。”

S.Katano, Y.Ueda, A.Hayashi and N.Mori: "Phase Transitions and Superconductivity of Sr-substituted La_<2-x>Ba_xCuO_4 (x=0.125)" Physica B. 213 & 214. 81-83 (1995)

S.Katano、Y.Ueda、A.Hayashi 和 N.Mori：“Sr 取代的 La_<2-x>Ba_xCuO_4 (x=0.125) 的相变和超导性”Physica B. 213

Y.Oka, T.Yao, N.Yamamoto, Y.Ueda, S.Kawasaki, M.Azuma and M.Takano: "Hydrothermal Synthesis, Crystal Structure, and Magnetic Properties of FeVO_4-II." J.Solid State Chem.123. 54-59 (1996)

Y.Oka、T.Yao、N.Yamamoto、Y.Ueda、S.Kawasaki、M.Azuma 和 M.Takano：“FeVO_4-II 的水热合成、晶体结构和磁性。”

A.I.Rykov: "NMR and Magnetic Susceptibility in Superconducting and Antiferromagnetic Ga-based Cuprates Y_<1-x>Ca_xSr_2Cu_2GaO_7 (0【less than or equal】x【less than or equal】0.3)" Physica C. 257. 86-98 (1996)

A.I.Rykov：《超导和反铁磁性镓基铜酸盐 Y_<1-x>Ca_xSr_2Cu_2GaO_7（0【小于等于】x【小于等于】0.3）中的核磁共振和磁化率”Physica C. 257. 86-98（ 1996）

Hiroyasu Tamura: "Phase Diagram of La_2NiO_<4+δ> (0【less than or equal】δ【less than or equal】0.18).II.Thermodynamics of Excess Oxygen,Phase Transitions and Phase Segregat " Physica C. 258. 61-71 (1996)

Hiroyasu Tamura：“La_2NiO_<4+δ>的相图（0【小于等于】δ【小于等于】0.18）.II.过量氧的热力学、相变和相分离” Physica C. 258. 61 -71 (1996)