Crystal structure and superconductivity in Ba₂Y_1-xPr_xCu₃O_7-y

Crystal structures and superconductive properties of the solid solution Ba₂Y_1-xPr_xCu₃O_7-y (0≤x≤1) are studied. Although Ba₂Y_1-xPr_xCu₃O_7-y has an orthorhombic structure which is isomorphic with Ba₂YCu₃O_7-y, T_c decreases monotonically with increasing Pr concentration, and superconductivity disappears at around x=0.6. The Rietveld analysis of X-ray powder diffraction data shows that both Cu(1)-O(3) bond length and the structural asymmetry of the Cu(2)O₂ planes increase by the infstitution of Pr for Y. Such structural changes induce the carrier density reduction and localization effects, which may cause the suppression of superconductivity in this system.