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

The formation temperatures of Bi1.6Pb0.4Sr2Ca2Cu3O10+x (Bi(Pb)-2223) and Bi1.6Pb0.4Sr2CaCu2O8+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. (C) 2000 Elsevier Science B.V. All rights reserved.