Studies on the Thermal Behavior of Ba2YCu3O7-x by X-Ray Powder Diffraction Method

Abstract

Thermal behavior of Ba₂YCu₃O_7-x was investigated mainly by X-ray powder diffraction method between 70 K and 1173 K. Oxygen-rich(x∼0.5) specimen is orthorhombic in symmetry in the temperature range between 70 K and 943 K. It undergoes a phase transition to tetragonal form at 943 K or 783 K in air or N₂ gas, respectively. On the other hand, oxygen-poor specimen(x∼1.0) semiconductive down to 4.2 k is tetragonal up to 1173 K in N₂ gas. Thermal expansion coefficient of a cell parameter is about 1.1 × 10^-5 K^-1 and that of c cell parameter is 2.5 × 10^,,5 K^-1, in air.