Subsolidus phase relationships and superconductivity in the Gd2O3-BaO-CuO system

Abstract
The 960 degrees C subsolidus phase relationships in the Gd2O3-BaO-CuO system were determined by means of X-ray diffraction as well as superconductive properties measurements. In the measured partial diagram, two ternary compounds occur: GdBa2Cu3O7-y and Gd2BaCuO5. GdBa2Cu3O7-y has an orthorhombic distorted perovskite structure with a=3.909 AA, b=3.847 AA and c=11.682 AA. It has a high-Tc superconductive phase with a zero resistivity transition temperature of 94.5 K. Gd2BaCuO5 also has an orthorhombic structure with a=7.225 AA, b=12.316 AA and c=5.722 AA. The possible space group is either Pbbm or Pbn2. Only the compound GdBa2Cu3O7-y is superconducting under the condition employed. The relationships between composition and superconductivity are also reported.