Enhanced critical current density in Nb3Al superconductor by optimizing mechanical alloying and subsequent sintering process

Abstract

The critical current density (Jc) is one of the most important properties for the practical application of Nb3Al superconductors. In this work, Nb3Al bulk superconductors were synthesized by mechanical alloying (MA) and subsequent sintering process. And its Jc performance is improved through optimizing the process parameters including ball milling time, sintering temperature and holding time. The results show that the optimal ball milling time to acquire high Jc performance was 20 h. Excessive ball milling worsened Nb3Al's Jc performance because some impurities were introduced into sintered sample. The holding time during sintering process mainly affected the grain size of Nb3Al. Some fine grains coalesce into larger ones after long time sintering. Besides, the sintering temperature and the holding time were all of significance to the grain connectivity in Nb3Al. Higher sintering temperature and longer holding time made a better grain connectivity. The highest Jc value of Nb3Al bulk was 2.5 × 104 A/cm2 (4.2 K, 6 T) with the sintering condition of 850 °C for 5 h. Our work raises some valuable discussions for the following studies on Nb3Al superconductor.