EFFECTS OF STOICHIOMETRIC VARIATION AND COOLING RATE ON THE PHASE-FORMATION AND CRITICAL-CURRENT DENSITY OF BI-2223 POWDER-IN-TUBE TAPES MADE FROM AEROSOL PRECURSOR

Powder-in-tube Bi-2223 is currently the most promising high-temperatur e superconductor that can be fabricated in long lengths by industrial processes, and is likely to be used as the conductor component in firs t-generation applications. Intensive investigations of these conductor s have revealed that the critical current density of fully processed t apes is influenced by a large number of processing parameters. Among t hese are the thermomechanical processing schedule and the extent of Bi -2223 phase conversion. These parameters are, in turn, affected by the precursor stoichiometry. In this study, powder precursors with varyin g Cu content were prepared using an aerosol pyrolysis technique, and p owder-in-tube conductors were fabricated using these precursors. Both fast and slow cooling rates were employed during thermomechanical proc essing, and different treatment schedules are correlated to the critic al current density. The results indicate that the effect of excess Cu on J(c) is minor compared to the large J(c) enhancements obtained by e mploying one or more slow-cooling steps in the thermomechanical proces sing schedule.