Improvement of critical current density in Nb3Al superconductors co-doped by Sn-B

In this paper, we innovatively introduced Sn and B into the Nb-Al system at the same time and successfully prepared high-performance Nb3Al bulks through mechanical alloying and subsequent low-temperature sintering processes. The influence of different doping amounts of B in the Sn-B co-doping on the superconducting properties of Nb3Al superconductors was also investigated. It was found that Sn-B co-doping greatly improves the superconducting properties of Nb3Al, especially the Jcproperties, compared with the undoped sample. The optimal doping amount of Sn-B co-doping is finally determined to be 4 at% Sn-2.6 at% B. At this time, the superconducting transition temperature of Nb3Al is up to 16.2 K, and the critical current density reaches up to 1.3 x 105 A & sdot;cm-2 (4.2 K, 5 T), which is almost twice higher than that of Sn-doped Nb3Al, and one order of magnitude higher than that of general undoped Nb3Al. Combined with the phase composition analysis and microstructure observation, we find that with the co-doping of Sn and B, the grain size of Nb3Al is refined, and the diffusely distributed Nb2Al nanoparticles are introduced, which greatly enhance the magnetic flux pinning effect of Nb3Al. Secondly, the intergranular connectivity of Nb3Al is significantly improved. The Sn-B co-doped Nb3Al superconductors combine the advantages of Sn doping to enhance flux pinning and B doping to improve intergranular connectivity, which synergistically promotes the dramatic improvement of Nb3Al superconductivity Nb3Al.