Control of oxygen release from Bi-2212 phase in a partial melt process

Abstract

A serious problem for Ag-sheathed Bi-2212 wires produced by a partial melt process is oxygen release which causes effluence of the oxide materials out of the Ag sheath. Released oxygen content for the Bi2Sr2Ca1Cu2AgxOy (x=0, 0.2 and 0.4) was evaluated by the TGA weight change during the partial melt process. It was found that (i) the powders released less oxygen when they are calcined at temperatures closer to the melting point, despite the calcining atmosphere and (ii) the addition of 0.2 mol Ag and higher oxygen partial pressure in the partial melt process are effective for reducing oxygen release. The reduction in released oxygen content was attributed to the doped Ag becoming liquid at the partial melting temperature of the Bi-2212 phase and the Ag liquid accommodating the released oxygen.