Ag-clad Bi-Sr-Ca-Cu-O wires: I. Phase study of fully processed 2:2:1:2 wires

Abstract We have studied the composition of phases in fully processed Ag-clad wires containing Bi-Sr-Ca-Cu-O with a starting cation ratio of 2:2:1:2 using electron probe microanalysis. Wires that were processed at temperatures not exceeding 850°C contained two phases: the two-CuO 2 layer superconductor (“2212”) and Bi 0.06 Sr 8.87 Ca 4.87 Cu 24 O x , which is a member of the “ 14 24 ” solid solution that is in equilibrium with “2212” at 850°C. Phases identified in wires melt processed at temperatures up to 920°C then annealed at 830–840°C were “2212”, (Sr 1− x Ca x )CuO 2 , and Ag particles. This appears to be a nonequilibrium phase assemblage as the superconductor is not reported to be in equilibrium with (Sr 1− x Ca x )CuO 2 at 800–850°C.