Preparation and Properties of Three Types of Orthorhombic Superconductor Ba2YCu3-xO7-y

Abstract
Three types of the orthorhombic superconductor were recognized based on crystallographic data; they were prepared in air by annealing coarse-grained Ba2YCu3-x O7-x at different temperatures before quenching into air. Annealing at higher temperature produced the superconductor with larger c cell dimension. The c cell dimension at room temperature showed a strong correlation with superconductivity. Superconducting transition temperature increases abruptly with decreasing c cell dimension in the range of 11.71 to 11.68 Å. The c cell dimension is about 11.70 Å for the superconductor exhibited zero resistance at 77 K.