Fabrication and superconducting properties of ex-situ PIT processed A15 type tape conductors

We fabricated three kinds of A15-type superconducting tapes by applying ex situ Powder-In-Tube method. Nb/sub 3/Sn, Nb/sub 3/Al, or V/sub 3/Si superconducting powder was tightly packed into a stainless steel (SUS 316) tube or a Cu-10wt%Ni tube. These tubes were cold-rolled into tapes. All tapes showed substantial J/sub c/ values at 4.2 K without any heat treatment. The SUS 316 tube with superior mechanical hardness was effective for obtaining high density A15 cores and realizing high J/sub c/ values although T/sub c/ values were depressed by the lattice distortion. Annealing after cold rolling recovered T/sub c/ values and enhanced J/sub c/ values of all three kinds of tapes. J/sub c/ increased with increasing annealing temperature. More than two orders of magnitude higher J/sub c/ values were obtained for Nb/sub 3/Sn and V/sub 3/Si tapes after the annealing at 900/spl deg/C, while the J/sub c/ enhancement of Nb/sub 3/Al tape was smaller than one order of magnitude. This difference of J/sub c/ enhancement can be explained by the difference of microstructural change by the annealing. The field dependence of J/sub c/ decreased with increasing annealing temperature, which can also be explained by the recovery of T/sub c/.