Overpressure processing Bi2223/Ag tapes

We report on the effect of overpressure processing on the electromagnetic properties and microstructure of monocore and multifilamentary Bi2223/Ag tapes. Samples at various stages of the usual thermo-mechanical processing for Bi2223/Ag tapes (from as-rolled to fully processed) were subjected to annealing at 815-820/spl deg/C for 18-108 h in a static Ar+O/sub 2/ atmosphere at the overall pressure 17.5/spl plusmn/0.5 MPa (pO/sub 2/= 0.003-0.02 MPa). Density measurements, microhardness tests, and SEM examination of polished sections reveal a notable densification of overpressure-processed samples. For partly reacted (so called HT1) samples, we found that overpressure processing for 36 h is sufficient to densify the Bi2223 core from 70/spl plusmn/5 to 87/spl plusmn/4% theoretical density and increase self-field J/sub c/(77 K) from 8/spl plusmn/1 to 30/spl plusmn/5 kA/cm/sup 2/ The results show that one-step processing of Bi2223/Ag tapes is possible.