Critical Current Density and Flux Creep in Melt-Processed Bi-Pb-Sr-Ca-Cu-O Superconductors

Abstract

We investigated the critical current density and the flux creep in melt-processed Bi-Pb-Sr-Ca-Cu-O for the purpose of studying the existence of strong flux pinning forces due to normal conducting precipitates. We fabricated samples with a similar microstructure to melt-processed Y-Ba-Cu-O and Tl-Sr-Ca-Cu-O having a strong pinning force. When the matrix was (Bi, Pb) 2 Sr 2 Ca 1 Cu 2 O y (2212) phase, the irreversibility field B irr was expressed as B irr \propt(1- T / T c ) 3/2 , which suggested that the expected flux pinning was due to normal conducting precipitates. A part of the matrix was transformed to (2223) phase by the postannealing of the sample; however, the superconducting properties were inferior to those observed in (2223) polycrystals.