Formation and Electrical Property of a High-Tc Phase Bi,Pb-Sr-Ca-Cu-O Superconductor

The influence of the sintering time on the formation of high-Tc phase and the electrical property has been studied for the sample with a nominal composition of Bi:Pb:Sr:Ca:Cu=0.96:0.24:1.0:1.1:1.6. The volume ratio of the high-Tc phase to the superconductive phases was approximately 85% by the heat treatment at 850°C for 48h, while the almost single high-Tc phase was obtained by repeating sintering procedures. The high-Tc phase particles were grown up to be about l0um in width for 48h, and after then the particle size remained almost constant. This tendency corresponds to the change in the volume ratio of the high-Tc phase on the heat treatment. As sintering time extended, Pb content decreased. The sample heat treated at 850°C for 200h had only 6% of its initial Pb content. The electrical resistance dropped to zero at 110K within the experimental limit of 10^-6 ohm in the sample heat treated at 850°C for 150h in air. However, the samples heat treated for 200h or more showed tailing in R-T curves.