Critical current density for Bi2Sr2CaCu2Ox/Ag tapes prepared using an isothermal partial melting method under controlled atmospheres

Bi2Sr2CaCu2O2 (Bi-2212)/Ag tapes have been prepared using an isothermal partial melting method under controlled atmospheres, in which partial melting and solidification have been carried out at the same temperature 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, solidification 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 using 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) at 4.2 K under 0 T for tapes of t(s) greater than or equal to 24 h at 865 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 the preparation of pure Bi-2212 tapes with high J(c).