Chemical and Mechanical Stability of High-Tc Phase in the Bi-Pb-Sr-Ca-Cu-o System(I)

Effects of Heat Treatment of Crushed Powder of the High-Tc Phase

Abstract

Chemical and mechanical stability of the high-Tc phase has been studied for the samples of Bi_0.9Pb_0.2Sr_1.0Ca_1.0Cu_1.6O_x. Mechanical grinding converts the high-Tc phase into a nonsuperconducting amorphous phase. The ground high-Tc phase is not stabilized on annealing at lower temperatures below 820°C. Annealing at lower temperature leads to precipitation of some impurity phases and the low-Tc phase which depends on annealing temperature and time. The high-Tc phase is recovered by annealing at 850°C. The lattice parameters a and c of the high-Tc phase annealed at 850°C are longer than those below 820°C.