Rapid-heating, quenching and annealing treatment for Nb3Sn superconductors with oxide particle addition

In this paper, different nanosize oxides doped Nb3Sn superconducting wires were prepared by the rapid heating quenching, and annealing (RHQA) process. Their crystal phase, microstructure, grain size, and superconducting properties were investigated. After the RHQA process, all samples exhibit a distinct Nb3Sn A15 superconducting phase. The oxide doped Nb3Sn samples have a more uniform and thicker Nb3Sn layer with significantly refined grain size. The prepared samples have superconducting transition at about 18 K. The critical current density (Jc) of the oxide-doped Nb3Sn wires is significantly enhanced. For the nano-size SnO2-doped Nb3Sn, the Jc reaches 7.73 x 104 A/cm2 at 4.2 K, 12 T, which is 70 % higher than the pure sample prepared by direct sintering at 800 degrees C; And the Jc is five-times higher than the pure sample at 10 K, 10 T. Improvement of Jc may be attributed to the suppression of grain size to 400-500 nm in the RHQ treatment because of nanoparticles which also act as additional point pinning centers. At high field, the low Tc superconducting phase with low irreversible field change to the normal state, which causes Delta kappa pinning and an increase in the Jc performance of superconductor