CRITICAL-CURRENT DENSITY FOR BI2SR2CACU2OX AG TAPES PREPARED USING ANISOTHERMAL PARTIAL MELTING METHOD UNDER CONTROLLED ATMOSPHERES/

Bi2Sr2CaCu2O2 (Bi-2212)/Ag tapes have been prepared using an isotherma l partial melting method under controlled atmospheres, in which partia l melting and solidification have been carried out at the same tempera ture but under different atmospheres. After melting the Bi-2212 powder in an N-2 gas flow (O-2 partial pressure, P(O-2) = 0%) for 5 min, sol idification has been carried out in an atmosphere of P(O-2) = 20% for 6-36 h. The critical current density (J(c)) of the prepared tapes usin g this method depends on the solidification time (t(s)) of the Bi-2212 phase after partial melting. J(c) is as high as 3.0 X 10(5) A/cm(2) a t 4.2 K under 0 T for tapes of t(s) greater than or equal to 24 h at 8 65 degrees C, but is limited to 1.0 x 10(5) A/cm(2) for tapes of t(s) = 12 and 18 h. It is found that t(s) is the most important factor in t he preparation of pure Bi-2212 tapes with high J(c).