Evolution of 2223 phase in the Bi₂Pb_0.6Sr₂Ca₂Cu_3.1O_y system

Abstract

The role of cationic ratios (Sr/Ca and Bi/Pb) in the evolution of high-T_c phase (2223) in samples prepared under different sintering conditions, starting with a composition of Bi₂Pb_0.6Sr₂Ca₂Cu_3.1O_y, has been investigated by employing energy-dispersive X-ray analysis, scanning electron microscopy and X-ray diffraction. As manifested by the observed decrease in Sr/Ca ratio, an increase in sintering temperature from 822 to 852 °C increases the disorder in Sr-O and Ca layers. The observed increase in the volume fraction of 2223 phase and the contraction in c-axis parameter have been explained on the basis of the observed decrease in Sr/Ca ratio. It thus appears that the disorder caused by the intersubstitution of Ca and Sr in SrO and Ca layers and partial replacement of Bi by Pb in the structure promote the evolution and growth of 2223 phase.