Nb/sub 3/Sn artificial pinning microstructures

Extension of the APC approach to Nb/sub 3/Sn requires that a second phase be incorporated into the Nb/sub 3/Sn layer. The second phase would increase pinning strength by either reducing the grain size or by the second phase pinning the flux itself. The following criteria for elements to be candidates for the APC approach are: (1) they must form intermetallic compounds with Cu or Sn and (2) they must have negligible solubility in Cu and Nb or they must be strong oxide formers. Many of the rare earth elements satisfy these criteria. To circumvent the large strains required to produce wires with a fine distribution of the second phase, film deposition techniques have been used. Critical current densities for Nb films doped with Ti and Y are about 4000 A/mm/sup 2/ at 6T and 4.2K.