Limiting Factors of Critical Current for Bi-Pb-Sr-Ca-Cu-O Oxide Superconductor

Critical current limiting factors for Bi-Pb-Sr-Ca-Cu-O oxide superconductor were investigated. A mixture of the oxide powders with a composition of Bi1.84Pb0.34Sr1.9Ca2.0Cu3.1Ox was calcined and the powders were placed in silver tubes. The tubes were processed by drawing and rolling to give resulted in 0.3mm thick tapes. The tapes were annealed at 825–843°C for 300h with intermediate pressing. Different annealing temperatures gave three types of samples with different microstructures. The critical current density Jc of the samples depended on the kind of foreign phases such as the Cu free (Bi,Pb)-(Sr,Ca)-O phase or 2201 phase as well as the a-b plane orientation. The weak link structure of the samples was an S-N-S junction regardless of the annealing conditions.