Microfilamentary conductor based on Bi(2212)

A series of ex situ prepared microfilamentary conductors has been prepared to determine the optimum heat treatment sequence for the development of a strain-tolerant microfilamentary conductor based on Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8- delta /. Both monolithic tapes and the microfilamentary composites were prepared so that the difference between the two methods for the same heat treatment could be evaluated. The monolithic tapes are easy to fabricate and are used to provide a rough guide to the desired degree of melting and the optimum oxygen concentration needed for the highest critical current densities. One of the ex situ microfilamentary composites showed a critical current density of 5000 A/cm/sup 2/ at 4.2 K while subjected to a strain exceeding 1%.