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 Nb 3 Al 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 Nb 3 Al superconductors was also investigated. It was found that Sn-B co-doping greatly improves the superconducting properties of Nb 3 Al, especially the J c properties, 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 Nb 3 Al is up to 16.2 K, and the critical current density reaches up to 1.3 × 10 5 A⋅cm −2 (4.2 K, 5 T), which is almost twice higher than that of Sn-doped Nb 3 Al, and one order of magnitude higher than that of general undoped Nb 3 Al. Combined with the phase composition analysis and microstructure observation, we find that with the co-doping of Sn and B, the grain size of Nb 3 Al is refined, and the diffusely distributed Nb 2 Al nanoparticles are introduced, which greatly enhance the magnetic flux pinning effect of Nb 3 Al. Secondly, the intergranular connectivity of Nb 3 Al is significantly improved. The Sn-B co-doped Nb 3 Al 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 Nb 3 Al superconductivity Nb 3 Al.