Improved superconducting Nb/sub 3/Sn wire using Nb(Ti), Sn(Ga), Cu, and Ag powders

摘要

Superconducting Nb/sub 3/Sn wire was produced by means of the powder metallurgy process using Nb-2.9 at.% Ti and Sn-6.2 at.% Ga powders to which small quantities of Cu, Ag or Cu+Ag powders were added. Using heat treatments at 950 degrees C and 750 degrees C, these additions increased the overall critical current density to 10/sup 8/ A/cm/sup 2/ at 22.8 T and 4.2 K. B/sub c2/ versus T measurements showed an increase in B/sub c2/ at temperatures of 6-18 K, of about 1 T, and T/sub c/ was increased by about 0.4 K. In a different wire annealed in a U-shape, the overall J/sub c/ at 23.5 T was 0.5*10/sup 8/ A/m/sup 2/ at 4.2 K, 1.4*10/sup 8/ A/cm/sup 2/ at 2.5 K, and 1.9*10/sup 8/ A/m/sup 2/ at 1.6 K. n-values were measured at fields up to 23 T. The different chemical activities of Ga and Sn when dissolved in Cu are discussed.