Subsolidus Phase Equilibrium in the System Y₂O₃-BaO-CuO at 900°C in Air

Abstract

The subsolidus phase equilibrium in the Y₂O₃-BaO-CuO system at 900°C in air was determined by solid-state reaction techniques and the powder x-ray diffraction method. The system was found to contain three quaternary compounds, i.e. YBa₂Cu₃O_x, Y₂BaCuO₅, and a perovskite like solid solution having a composition of Y₂xBa₂-xCuOδ whose x ranges from 0.07 to 0.25. The structural symmetry of the last material changes from tetra-gonal → orthorhombic → tetragonal as x increases. Furthermore, a new ternary compound Ba2CuOx has been isolated whose structure is tetragonal K₂NiF₄ type with lattice parameters a=3.988A and c=12.988A.