Effects of heating temperature and atmosphere on critical current density of Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/Ag/sub 0.8/O/sub y/ Ag-sheathed tapes

In partial melt processing of Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/Ag/sub 0.8/O/sub y/ silver sheathed tapes, the effects of heating temperature and atmosphere on the critical current density, J/sub c/, were studied. It was found that J/sub c/ is higher for the samples treated in pure oxygen than those in air and has the maximum value at a heating temperature of 885 degrees C. During partial melting, nonsuperconducting Sr-Ca-Cu-O precipitates grew in size with increasing temperature and caused a decrease of J/sub c/. The composition of the Sr-Ca-Cu-O phases in the tapes treated at 885 degrees C was (Sr,Ca)/sub 1/Cu/sub 1/O/sub y/ in air and (Sr,Ca)/sub 3/Cu/sub 5/O/sub y/ in oxygen. The size of precipitates in oxygen was smaller than in air. The highest J/sub c/ value, 1.2*10/sup 5/ A/cm/sup 2/ at 8 T and 4.2 K, was achieved in oxygen.<
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