High critical current Ag and Ag alloy sheathed multifilament Bi-2223 tapes

Ag sheathed (BiPb/sub 2/)Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ (Bi-2223) multifilament tapes with filament numbers of 19, 37, 55, and 85 were produced by the powder-in-tube method. Enhanced tape performance has been achieved by optimisation of the processing conditions. Key factors are addressed that include elimination of the 2212 phase, improving grain connectivity through reducing the 2201 phase and alkaline earth cuprate phases, increasing superconductor core density as well as enhancing current contribution from edge filaments. A high J/sub c/ of 50 kA/cm/sup 2/ with an I/sub c/ of 42 A has been achieved reproducibly in 19 filament tapes with dimensions of 0.16/spl times/2.8 mm/sup 2/ and silver/superconductor ratios of 4.4:1. By reducing the silver ratio, a J/sub e/ of 14 kA/cm/sup 2/ with an I/sub c/ of 48 A has been obtained in 55 filament tapes and an I/sub c/ of 84 A has been obtained in a tape with dimensions of 4/spl times/0.23 mm/sup 2/. A record J/sub c/ of more than 30 kA/cm/sup 2/ with an I/sub c/ of 32 A was achieved in 250 metres long standard tapes. A 1250 m long pure Ag sheathed tape and an 1100 m long Ag alloyed tape have been produced with a J/sub c/ of higher than 25 kA/cm/sup 2/ by using optimised process parameters.

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