Fabrication of (Bi,Pb)-2223/Ag-Cu alloy sheathed tapes: optimization of Cucomposition in the sheath with respect to the Cu stoichiometry in the system

(Bi,Pb)-2223/Ag-Cu alloy sheathed tapes with varying Cu compositions (3, 6, 9 and 12 at.%) in the sheath have been fabricated by powder in tube (PIT) technique using rolling as the deformation step. Two precursor powders with Cu stoichiometries of 3.0 and 3.2 were used to prepare (Bi,Pb)-2223/Ag-Cu alloy sheathed tapes. Phase evolution study by means of XRD and critical cu rrent density (J(c)) measurements at 77 K, 0 T have been used to elucidate the performance of the tapes and to determine the optimum Cu doping level i n the sheath with respect to the Cu stoichiometry in the system. It was fou nd that the level of Cu doping in the sheath is dependent on the Cu stoichi ometry in the system. A doping level of 6 at.% is found to be the optimum f or the Cu stoichiometry of 3.0 in the system with regard to the Bi-2223 pha se growth, the ultimate Bi-2223 phase fraction and the critical current den sity (J(c)). Alloy sheathed tapes using the precursor with a Cu stoichiomet ry of 3.2 is found to yield inferior superconducting properties especially when the doping level of Cu exceeds 3 at.%. (C) 1999 Elsevier Science B.V. All rights reserved.