Formation of the High-T_c Phase in Rapidly Quenched Bi-Pb-Sr-Ca-Cu-O Ceramics

Abstract

Amorphous ceramics with the composition of Bi 2 Pb 0.4 Sr 2 Ca 2 Cu 3 O y were prepared by rapid quenching. The change in crystalline structure during annealing and the effect of the “seeding” with the high- T c phase were investigated. The volume fraction of the high- T c phase increases with annealing time; however, the low- T c phase reaches a maximum value of 38% for 1 h annealing and decreases on prolonged annealing. The formation rate of the high- T c phase changes when the volume of the high- T c phase reaches about 30%. TEM observation shows that the high- T c phase is often located between the low- T c phase and the nonsuperconducting phase. The addition of the seed crystals with the high- T c phase is effective in forming the high- T c phase in shorter annealing times, but a smaller volume fraction of the high- T c phase was obtained after annealing for 50 h.