Effects of the time sequence of the cold rolling on the processing time of Ag-alloy sheathed (Bi,Pb)(2)Sr2Ca2Cu3Ox tapes

The effect of the time sequence of cold working/sintering on the transport J(c) has been studied. The results on the variation of J(c) with sintering time between the first and second intermediate cold rolling, t(s2), are presented. We have found that J(c) peaks sharply at an optimum t(s2). For example, tapes with a total sintering time of 140 h reach an optimum J(c) of 2.1 x 10(4) A cm(-2) (77 K, self-field) at t(s2) = 27 h. In general, there is a narrow window of optimisation in t(s2); in this example, J(c) drops by 50% within 7 h of the optimised value. We have also found that the optimum total sintering time (t(tot)) for a tape increases gradually with t(s2) e.g. t(tot) < 90 h for t(s2) = 22 h and t(tot) > 180 h for t(s2) = 35 h. X-ray diffraction analysis (XRD) was used to correlate the phase conversion prior to the second intermediate rolling with the J(c). The results suggest that the total processing time can be adjusted by t(s2). This has important consequences on reducing the long processing time of BSCCO tapes.