Superconducting parameters of a Cu93Nb5Sn2 alloy

Whereas the as-cast alloys of the type Cu93Nb5Sn2 do not turn superconducting down to 4.5 K, cold-working and subsequent heat treatments are found to improve their superconducting parameters appreciably. Thus, cold-rolled strip (0.1 mm thick) annealed at 700degC for 11 hours under high vacuum shows a superconducting transition at 17degK, suggestive of the formation of the Nb3Sn phase during the heat treatment. The critical current density, Jsub(c), of the same sample measured at 4.2degK and in a magnetic field of 30 KOe is 4X104 Amps/cm2. These values of the superconducting parameters are significantly higher than those reported earlier by Tsuei. Alloys with large contents of copper (93%) are extremely ductile and are conveniently rolled into the form of strips as thin as 0.05 mm. For the same reason, these alloys should prove very stable in high magnetic fields. It should also be possible to raise Jsub(c) to values, comparable or even higher than that for Nb3Sn, either by varying heat treatments or by further adding suitable impurities. The cost of production of such materials is much lower than that for the conventional stabilized conductors. (author)