OVERPRESSURE PROCESSING OF AG-SHEATHED BI-2212 TAPES

A critical problem for melt-processed silversheathed Bi-2212 tapes is gas release during heat treatment which deforms the sheath (''bubbling '') and forms voids in the superconducting core. An overpressure furna ce is used to study how the extent of bubbling changes with the total pressure (P-tot), By processing in P-tot up to 9 atmospheres with cons tant oxygen partial pressure (pO(2) = 1 atm), bubbling in coils is eli minated, The critical current density increases with increasing P-tot Also, the phase assemblage in overpressure-processed tapes is unchange d compared to conventionally processed tapes.