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

Abstract

(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 current 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 in the sheath with respect to the Cu stoichiometry in the system. It was found that the level of Cu doping in the sheath is dependent on the Cu stoichiometry in the system. A doping level of 6 at.% is found to be the optimum for the Cu stoichiometry of 3.0 in the system with regard to the Bi-2223 phase growth, the ultimate Bi-2223 phase fraction and the critical current density ( J c). Alloy sheathed tapes using the precursor with a Cu stoichiometry of 3.2 is found to yield inferior superconducting properties especially when the doping level of Cu exceeds 3 at.%.