Temperature Variation of the Structural and Thermal Characteristics of YBa2Cu3O7-x in the Range from 90 to 400 K.

The X-ray studies of the tetragonal YBa2Cu3O7−x compound are performed at different temperatures from 400 to 90 K and the temperature variation of the thermal expansion coefficients and the Debye characteristic temperature is determined. The anisotropy of thermal expansion is investigated. It is found that the two dynamical characteristics monotonously decrease with temperature lowering whereas for the superconducting orthorhombic modification their temperature dependences are anomalous. The mean thermal expansion coefficient as well as the overall Debye temperature for the tetragonal phase are smaller than those for the orthorhombic one.FLWNA