Preparation of High-Tc Superconducting Bi-Ca-Sr-Cu-O Ceramics by the Melt Quenching Method

Abstract

Superconducting Bi-Ca-Sr-Cu-O ceramics with T _c(onset)=102 K and T _c(zero)=92 K were prepared by a melt quenching method, in which the melt of nominal composition BiCaSrCu₂O _x was first quenched and then annealed at 800∼850°C for 24 h in oxygen atmosphere. It was found that the rapidly cooled samples after annealing show high T _c and sharp superconducting transition, but the samples slowly cooled in the furnace after annealing show low T _c and broad transition with a tail. The critical current density at 77 K in the zero magnetic field for the rapidly cooled sample after annealing at 800°C was 102 A/cm².