Improvements in critical current densities of internal tin diffusion process Nb3Sn wires by additions of third elements

Improvements in critical current densities of internal tin diffusion process Nb3Sn multifilamentary wires have been attempted by indium and titanium additions. The Nb3Sn wires with the indium addition to the Sn core and the titanium addition to the Cu matrix have been fabricated. The indium addition increases critical current density (Jc) at each field compared with pure Nb3Sn wire, and Jc at higher fields increases with increasing filament diameter. An overall Jc of 6.2 × 10⁴A/cm²at 12T and 4.2K is obtained for the 4.2 μm-filament indium addition wire reacted at 750 °C-50h. The titanium addition increases the Nb3Sn layer growth rate and Jc in fields over 13T. An overall Jc of 3.0 ×10⁴A/cm²at 15T and 4.2K is obtained for the 11.7 μm-filament titanium addition wire. Moreover, the simultaneous indium addition to the titanium addition wire produces further improvement in Jc. The indium and titanium addition Nb3Sn wires are the most favorable superconductors for generating magnetic field over 10T.