Properties Comparison of RHQT Nb 3 (Al 0.95 Ge 0.05 ) Superconductors Formed via Quenched bcc Phase With/Without Disordered A15 Present

This work compared the properties of rapid heating, quenching, and transformation (RHQT) processed Nb 3 (Al 0.95 Ge 0.05 ) superconducting wires formed via quenched bcc phase with and without disordered A15 phase present. When using 45 μm Nb as raw material, the quenched wires consisted of a single bcc phase in contrast to both bcc and A15 phase presented in 5-μm Nb wires. After transformation process, all the fabricated Nb 3 (Al 0.95 Ge 0.05 ) superconductors are composed of A15 phase, showing higher T c of 18.2 K than the pure Nb 3 Al of 17.1 K. The smallest Δ T c value was 0.7 K for the Nb 3 (Al 0.95 Ge 0.05 ) superconductor using 45 μm Nb. Both layer J c and irreversible field ( B irr ) of 45-μm Nb superconductor are better than that of the 5-μm Nb samples, which can be attributed to higher density of stacking fault formed in the A15 phase transformed from bcc phase. Due to higher T c of Ge-doped sample, the layer J c and B irr performances of the best Nb 3 (Al 0.95 Ge 0.05 ) superconductor changes from strongly inferior to slightly superior compared to pure binary Nb 3 Al sample as increasing temperature from 4.2 to 12 K.