The formation temperatures of Bi(Pb)-2223 in partial vacuum

The formation temperatures of Bi 1.6Pb 0.4Sr 2Ca 2Cu 3O 10+ x (Bi(Pb)-2223) and Bi 1.6Pb 0.4Sr 2CaCu 2O 8+ y (Bi(Pb)-2212) in air, on silver substrates, at atmospheric pressure (1 atm) and partial vacuum (10 −1 and 10 −2 atm), were studied. At 1 atm, the formation window of Bi(Pb)-2223 resides within that of Bi(Pb)-2212 leading to the well-known intergrowth of the two phases. At lower pressures, the formation windows of Bi(Pb)-2223 shift to lower temperatures, allowing the preferred formation of Bi(Pb)-2223 free from the low T c phases, the 2212 variety and possibly also the 2201 one. Superconducting Bi(Pb)-2223 coated pure silver tapes, sintered at low atmospheric pressures and low temperatures, show enhanced critical current density by more than 40%. These sintering conditions also render the formation of Bi(Pb)-2223 less sensitive to temperature deviations from the optimal sintering temperature.