Effect of third-element additions on the upper critical field of bronze-processed Nb/sub 3/Sn

A direct measurement has been carried out of the upper critical magnetic field (B/sub c2/) of bronze-processed Nb/sub 3/Sn wires with and without the addition of various third-elements to the Cu-Sn matrix using a hybrid-magnet at the Tsukuba Magnet Laboratory at fields up to 30 T. The B/sub c2/ of pure Nb/sub 3/Sn rose with increasing heat treatment temperature up to 880/spl deg/C (B/sub c2/=24.7 T at 4.2 K), above which point it decreased rapidly. Its value was independent of the Sn content in the bronze. In the Ti addition samples, the optimum value of B/sub c2/ (=26 T at 4.2 K) depended on both Ti content and heat treatment temperature. When Sb was added, B/sub c2/ showed a sharp fall below a heat treatment of 700/spl deg/C due to the replacement at the Sn site by a Sb atom.