Grain boundary compositions, transport and flux pinning of multifilamentary Nb/sub 3/Sn wires

The concentrations of elements at the grain boundaries and inside the grains of the A15 phase were measured in a variety of commercial and laboratory Nb/sub 3/Sn, (Nb,Ta)/sub 3/Sn and (Nb,Ti)/sub 3/Sn multifilamentary wires. Scanning Transmission Electron Microscopy (STEM) was used to determine the concentrations with high spatial resolution. The concentrations of Sn and Cu near the grain boundaries increased rapidly from their values inside the grains, while the Nb showed the opposite behavior. Ta substitutes Nb even near the grain boundary and Ti substitutes Nb and Sn. The results are compared with the EPMA analysis. Critical current densities in background fields of 2 to 23 tesla, B/sub c2/ versus temperature and T/sub c/ were measured for each sample.>