Stability of high T_c phase in Bi₂Pb_xSr₂Ca₂Cu_3.1O_y superconductor

Abstract

The effect of addition of Pb on zero resistance temperature, Tc (R=0), lattice parameters and stability of Bi₂Pb_xSr₂Ca₂Cu_3.1O_y superconductors is studied for x varying from 0.0 to 0.8 in the starting composition. The addition of Pb enhances the high Tc phase and a maximum Tc (R=0) of 105K is observed for the sample prepared with x=0.6. The lattice parameters of low and high Tc phases are a_L = 5.40Å, b_L = 5.42Å, c_L = 30.70 Å and a_H = 5.40 Å, b_H = 5.42 Å, c_H = 37.36 Å, respectively. A systematic variation in lattice parameters with addition of Pb has been observed. Lead containing samples exhibit a higher value of critical current (Ic) as well. On the basis of fractional changes in Ic and Tc (R=0) with exposure of superconducting sample to ambient conditions of atmosphere upto 50 days, it has been inferred that high Tc phase is most stable in the sample corresponding to 0.6Pb.