Further evidence that the critical current density of (Bi, Pb)2Sr2Ca2Cu3Ox silver-sheathed tapes is controlled by residual layers of (Bi, Pb)2Sr2CaCu2Oy at (001) twist boundaries

Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

“…Gurevich and Friesen 21 have shown that nonlinear effects on critical currents are due to removing dissipation obstructions in superconductors, some of which may be pores and grainboundary wetting phases. 2212 grains and intergrowths can play a very important role in limiting J c , as pointed out earlier by Umezawa et al 15 Evidently OP processing reduces all these obstructions and thus results in the J c increase in FHTϩOP samples. Present studies using local probes such as magneto-optical imaging are investigating the local current obstructions in exceptionally high J c samples such as these FHTϩOP samples.…”

“…Residual 2212, present as half-cell intergrowths in 2223 grains and as grains in 2223 colonies, was detected by multiple techniques in 2223 after HT2 or FHT. 2,15,16 Increases in J c were found to correlate strongly with decreases in the volume fraction of 2212. 2,10,15 A central question in further improving the performance of 2223 tapes is how to eliminate the current limiting mechanisms of porosity, cracks, and residual 2212 to further improve the J c .…”

Improving the critical current density in Bi-2223 wires via a reduction of the secondary phase content

“…Note the high density of intergrowths in the Bi-2223 grain which is furthest away from the amorphous phase. In the case of earlier studies [8], [9], 2212 was observed at the basal plane boundaries of the 2223 grains and correlated with an 80 K kink in the vs curve of unrolled, as-produced samples. There was a highly nonlinear increase in as the 2212 intergrowth and the kink was eliminated.…”

Critical current limiting factors in post annealed (Bi; Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ tapes

“…The critical current limiting mechanisms are many and complex in Bi-2223 tape [3], [4]. The key to high performance is to improve the electrical connectivity, which is compromised by weak flux pinning regions, by lower intergrowths [5], cracks or porosity [3], [4]. Slow cooling [6], two-step sintering [7], [8], and post anneal [9] have been found to improve the critical current density ( ).…”