Critical current density for Bi 2Sr 2CaCu 2O x/Ag tapes prepared using an isothermal partial melting method under controlled atmospheres

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Bi 2Sr 2CaCu 2O x (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, soliddification has been carried out in an atmosphere of P(O 2) = 20% for 6–36 h. The critical current density ( J c) is as high as 3.0 × 10 5 A/cm 2 at 4.2 K under 0 T for tapes of t s ≥ 24 h at 865°C, but is limited to 1.0 × 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.