Reduction in secondary phases and increased transport I(c) of (Bi,Pb)2223/Ag tapes sintered with rapid heating rates

Young, E.A., Yang, Y., Lehmann, M., Riddle, R. and Beduz, C. (2003) Reduction in secondary phases and increased transport I(c) of (Bi,Pb)2223/Ag tapes sintered with rapid heating rates. IEEE Transactions on Applied Superconductivity, 13 (2), 2941-2944. (doi:10.1109/TASC.2003.812062).

Abstract

In a two-step heat treatment with one intermediate rolling the final transport critical current, (I_c at 77 K, self field, 1iV/cm), of 37 filament (Bi,Pb)2223/Ag tapes increases linearly with the heating ramp rate: 20 A to 40 A, (~20,000 Acm^-2), for 20°C/hour to 400°C/hour. The principle benefit of the rapid ramp rate is likely to come from ramping fast though 800°C to 832°C in the 1st heat treatment. SEM and XRD analysis on the superconductor-Ag interface show a decrease in the amount of secondary phases, Cu₂O, Bi₂(Sr,Ca)₂Cu₁O_x, Bi(Sr,Ca)O_x, with increasing ramp rate and critical current.

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