Improved high-field performance in Nb/sub 3/Sn conductor prepared from intermediate compound

Nb/sub 3/Sn superconductors have been fabricated using Nb/sub 6/Sn/sub 5/ intermediate compound powder synthesized by a melt diffusion process. The mixed powder of Nb/sub 6/Sn/sub 5/ and Nb was encased in a Ta tube, and then fabricated into a tape without intermediate annealing. A Cu sheath with a Ta barrier was also used for the fabrication. The Nb/sub 3/Sn tape shows a B/sub c1/ of 24.7 T at 4.2 K after the reaction at 900/spl deg/C. In addition the B/sub c2/ increased further by Ti doping. Moreover, the addition of 0.5-1.0 wt% Ge produces appreciable improvements in Tc and Jc at high magnetic fields. A Jc (Nb/sub 3/Sn) of 2.7/spl times/10/sup 4/ A/cm/sup 2/ has been obtained at 21 T and 4.2 K in the Ge-doped specimen. A small amount of Cu addition decreases the optimum reaction temperature to 800-850/spl deg/C. Present Nb/sub 3/Sn conductors seem to be useful for NMR high-field magnets as well as for refrigerator-cooled superconducting magnets.