Effect of short processing time on Bi-2223 phase formation kinetics and critical current in Bi-2223/Ag tapes

Abstract

Bi-2223 volume fraction and the critical current (I/sub C/) in Bi-2223/Ag tapes exhibited maximum values (f/sub 2223 max/ and I/sub Cmax/) versus sintering time; on further heating the Bi-2223 phase decomposed and the I/sub C/ decreased. The total time to reach I/sub Cmax/ is defined as t/sub c/. Based on the investigation of the effect of processing on Bi-2223 phase formation kinetics, an optimal processing to substantially reduce the processing time in Ag-sheathed Bi-2223 tapes was introduced in this paper. It was found that, after 10-15 h sintering, the Bi-2223 phase formation rate decreased. An intermediate procedure using quench, pressing or rolling and then rapid heating can avoid unnecessary Bi-2223 phase decomposition and recovery, decrease the diffusion distance and substantially reduce the sintering time in Bi-2223/Ag tapes. The t/sub c/ was reduced to 30 h or even 20 h and J/sub c/ reached 40-50 kA/cm/sup 2/ for multifilamentary tapes. Our results indicated that Pb distribution in precursor powder plays an important role on fast phase formation. Fabrication of high J/sub c/ tapes in a short time is desirable to scale-up production of Ag/Bi2223 tapes.