Preparation of Bi-2223/Ag tapes with pre-annealed precursor powders

Several kinds of precursor powders with varied phase assemblages were prepared by pre-annealing the commercial BSCCO 2223 powders in pure Ar, O2 or mixed gas (7.5% O2 + 92.5% Ar) at elevated temperatures, and then were made into monofilament Bi-2223/Ag tapes. Annealing the powders in pure Ar at 700 deg. C for 10 h greatly retarded the 2223 phase formation at the initial reaction stage, consequently lowered the J c value of the fully processed Bi-2223/Ag tapes. The sample fabricated by using the precursor powder pre-annealed in 7.5% O2 showed the best J c property (25 kA/cm2, 77 K, 0 T). The microstructures of the samples made from various precursor powders were examined, which were correlated to their different phase formation behaviors and transport properties