Crystal Structures and Superconductivity in EuxBa3-xCu₃Oy (1≤x≤1.5)

The Eu x Ba 3- x Cu 3 O y system has been investigated by X-ray powder diffraction analysis and electrical resistivity measurements. The region of solid solubility for Eu x Ba 3- x Cu 3 O y has been found to extend from x = 1.0 (the 123 phase) to x = 1.5 (the 336 phase). As x increases, the phase changes from orthorhombic to tetragonal around x = 1.25, resulting in a less metallic and lower T c . Even in the tetragonal phase samples, at x = 1.25 and 1.33, superconductivity has been observed.