HIGH-FIELD A-15 SUPERCONDUCTORS PREPARED FROM INTERMEDIATE COMPOUND

A15 Nb-3(Al,Ge) and Nb3Sn have been easily synthesized starting from N b-2(Al,Ge) and Nb6Sn5 intermediate compound powder, respectively. The intermediate compound powder was mixed with Nb powder by a ball mill i n Ar atmosphere. The mixed powder was encased in a Nb or Ta tube, and then fabricated into a tape without intermediate annealing. The mechan ical mixing of powders promotes the formation of A15 phase in subseque nt reaction treatment. The bulk sintered specimens show higher onset T e but broader Te transition than tape specimens. In the Nb-3(Al,Ge) ta pe reacted at 1300 degrees C, a Jc of over 2.7 X 10(4) A/cm(2) has bee n obtained at 4.2K and 23T. The addition of MgO powder enhances Je and reduces the peak effect in the Nb-3(AT,Ge) tape. The Te of Nb3Sn tape prepared by present process is appreciably higher than that of bronze - processed Nb3Sn. Even pure Nb3Sn tape shows Bc(2) Of nearly 25T at 4.2K after the reaction at 900 degrees C. The present A15 Nb-3(Al,Ge) and Nb3Sn tapes seem to be promising for generating 20T at 4.2K.