Superconducting Wires Obtained by Bi‐2223 Coating, or Bi‐2223 Synthetization from Precursors, on a Metal Core

uperconducting wires have been prepared by Bi 1.6 Pb 0.4 Sr 2 Ca 2 Cu 3 O 10 (Bi-2223) coating of a great number of different metallic cores. The best electrical results (high T c0 and small ΔT c ) were obtained with silver and silver coated iron cores for a sintering temperature T s = 835 °C. For short sintering durations (less than 32 h) the resistance -versus-temperature curves R = f(T) presented several drops revealing the existence of several phases. In most cases one of these phases at least presents a large ΔT c value that can be estimated by a percolation based parametrization method. For very long sintering durations, up to six days, and with addition of an excess of PbO (the percentage of PbO in excess is related to the sintering duration), these curves presented only one drop. In the latter case T c 0 = 108 K, corresponding to 60% Bi-2223, as shown by the percolation based parametrization method. It has been shown also that it is not necessary to use a good Bi-2223 ceramic to obtain these results, even precursors can be used, the Bi-2223 coating being then synthesized on the silver core. The role of the substrate, sintering temperature and of the excess of PbO will be discussed.