Overpressure processing of Ag-sheathed Bi-2212 tapes

Abstract

A critical problem for melt-processed silver-sheathed Bi-2212 tapes is gas release during heat treatment which deforms the sheath ("bubbling") and forms voids in the superconducting core. An overpressure furnace is used to study how the extent of bubbling changes with the total pressure (P/sub tot/). By processing in P/sub tot/ up to 9 atmospheres with constant oxygen partial pressure (pO/sub 2/=1 atm), bubbling in coils is eliminated. The critical current density increases with increasing P/sub tot/. Also, the phase assemblage in overpressure-processed tapes is unchanged compared to conventionally processed tapes.