Effect of Cooling Rate on Critical Current Density for Bi₂Sr₂CaCu₂O_8+δ/Ag Composite Tapes

Abstract

Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212)/Ag composite tapes were prepared by melt-solidifying method and the relationship between cooling conditions after the melt-solidification and superconducting properties were investigated. A high cooling rate was found to be effective in suppressing the decomposition of Bi-2212 and in increasing J c . A tape with high J c of 2.4×10 5 A/cm 2 at 4.2 K in 12 T was obtained by fast cooling. With annealing of this tape in N 2 atmosphere, J c of 3.1×10 4 A/cm 2 at 77.3 K in 0 T was attained due to the enhancement of T c .