Abstract
In a two-step heat treatment with one intermediate rolling the final transport critical current, (I/sub c/ at 77 K, self field, 1/spl inodot//spl grave/V/cm), of 37 filament (Bi,Pb)2223/Ag tapes increases linearly with the heating ramp rate: 20 A to 40 A, (/spl sim/20,000 Acm/sup -2/), for 20/spl deg/C/hour to 400/spl deg/C/hour. The principle benefit of the rapid ramp rate is likely to come from ramping fast though 800/spl deg/C to 832/spl deg/C in the 1st heat treatment. SEM and XRD analysis on the superconductor-Ag interface show a decrease in the amount of secondary phases, Cu/sub 2/O, Bi/sub 2/(Sr,Ca)/sub 2/Cu/sub 1/O/sub x/, Bi(Sr,Ca)O/sub x/, with increasing ramp rate and critical current.
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