Configuration and Rearrangement Rate of Excess Oxygen Atoms in Transition-Metal Oxides Related to Superconductors

超导体相关过渡金属氧化物中过量氧原子的构型和重排率

基本信息

批准号：
08454208
负责人：
OGUNI Masaharu
金额：
$ 5.06万
依托单位：
Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

Both La_2NiO_<4+delta> and La_2CuO_<4+delta> crystals have atomic arrangements of a K_2NiF_4 type, and the latter crystal only with excess oxygen atoms shows superconductivity at low temperatures. The configurational structure and rearrangement rate of the excess oxygen atoms as functions of delta, affecting the superconducting properties in the latter copper crystals, are attractive. Heat capacity, resistivity and thermoelectric power were measured for the both crystals in the present work.1) High-precision adiabatic calorimeter was constructed which works in the temperature range between 13 K and 500 K.2) Nickel compound with delta=0.00 showed remarkable two-dimensional nature in the magnetic interaction between electronic spins of nickel atoms. The possibility was indicated that the phase transitions at 80 K and 120 K are of the (super-lattice commensurate) -incommensurate- (normal commensurate) type. It was also indicated that the crystals in the delta range between 0.047 and 0.150 show different delta-T phase relations depending on the size of crystal particles. Low-temperature stable compounds were found to be formed at around delta=0.07 and 0.10, and peritectic or eutectic disordering phenomena of excess oxygen atoms were found to take place in the delta ranges between the compositions of stable compounds. Glass transition phenomena due to the freezing-in of diffusional motion of excess oxygen atoms were found.3) Copper compounds with 0<delta<0.035 showed three structural phase transitions below 320 K.It was indicated that the phase separation with respect to the composition of excess oxygen atoms take place above room temperature, and that the phase transitions are ascribed to the tilt of CuO_6 octahedra. A glass transition was observed for delta-0.05 and 0.07 crystals, and interpreted as due to freezing of the short-range rearrangement (not diffusional motion) of excess oxygen atoms.

La_2nio_ <4+delta>和La_2cuo_ <4+delta>晶体具有K_2NIF_4类型的原子布置，而后一种晶体仅具有过量的氧原子显示出低温下的超导性。多余的氧原子的构型结构和重排速率作为三角洲的功能，影响后一种铜晶体中的超导性能。在目前的工作中，测量了两个晶体的热容量，电阻率和热电功率。1）构建高精度绝热量热仪，在13 K和500 k.2的温度范围内起作用，其在13 k和500 k.2）具有delta = 0.00的镍化合物在镍型镍型镍之间的磁相互作用中显示出显着的两维性质。可能性表明，在80 K和120 K处的相变是（超晶格） - 固定型（正常相称）类型。还表明，根据晶体颗粒的尺寸，增量范围为0.047至0.150之间的晶体显示不同的delta-t相位关系。发现低温稳定的化合物在三角洲= 0.07和0.10左右形成，并且发现多余的氧原子的直体或共骨无序无序现象发生在稳定化合物组成之间的三角洲范围内。 Glass transition phenomena due to the freezing-in of diffusional motion of excess oxygen atoms were found.3) Copper compounds with 0<delta<0.035 showed three structural phase transitions below 320 K.It was indicated that the phase separation with respect to the composition of excess oxygen atoms take place above room temperature, and that the phase transitions are ascribed to the tilt of CuO_6 octahedra.观察到Delta-0.05和0.07晶体的玻璃转变，并被解释为由于冻结了多余的氧原子的短距离重排（不是扩散运动）。