Pr-doping effect on the structure and superconductivity of Bi 2Sr 2Ca 1− xPr xCu 2O y single crystals

Abstract

Effect of Pr-doping on the structure and superconductivity of Bi2212 system was studied for Bi 2Sr 2Ca 1− x Pr x Cu 2O y single crystals with x=0–0.78. The a- and b-axis lengths increase with increasing Pr concentration, while the c-axis length and the period of modulation decrease with Pr-doping. These can be explained by the higher valence of Pr ion substituting at Ca site, the extra oxygen in BiO bilayers and the lattice mismatch between perovskite layer and BiO bilayer. In addition, the changes in lattice parameters are more dramatic in the Pr-rich region than those in the Ca-rich region, which can be attributed to the difficulty in the intercalation of extra oxygen in the BiO bilayer at high-doping level. The superconducting transition temperature increases slightly at first and then drops gradually upon Pr doping and the complete suppression of superconductivity occurs when the Pr content reaches 0.60. The superconducting volume faction also decreases with Pr content and is proportional to 1− ax 2.