Abstract The Nb3(Al1-xSnx) superconductors (x = 0.05, 0.15, 0.25, 0.35) were prepared by mechanical alloying and subsequent low-temperature sintering. It was found that the critical current density (Jc) of the obtained Nb3(Al1-xSnx) sample is enhanced significantly compared to undoped Nb3Al prepared using the same method. The maximum value of the Jc reaches up to 5.10 × 104 A·cm−2 (4.2 K, 5 T) for Nb3(Al0.85Sn0.15) sample. Combined with the phase composition analysis and microstructure observation, it is indicated that Sn enters the A15 crystal structure of Nb3Al forming the Nb3(Al1-xSnx) phase after low-temperature sintering. What's more, Sn doping improves the grain connectivity as well as refines the grain size of Nb3Al, which are the main reasons for the enhancement of Jc in the Sn doped samples. Based on the exploration of the phase evolution of Nb–Al–Sn system during the mechanical alloying and subsequent low-temperature sintering process, it is also confirmed that Nb3Sn forms firstly during the sintering process and then can serve as the perfect nucleus of Nb3Al to increase its nucleation rate, leading to the significant decrease of the grain size of Nb3Al.

中文翻译：

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Sn掺杂低温烧结Nb3Al超导体的临界电流密度增强

摘要 通过机械合金化和随后的低温烧结制备了 Nb3(Al1-xSnx) 超导体 (x = 0.05, 0.15, 0.25, 0.35)。发现与使用相同方法制备的未掺杂 Nb3Al 相比，获得的 Nb3(Al1-xSnx) 样品的临界电流密度 (Jc) 显着提高。对于 Nb3(Al0.85Sn0.15) 样品，Jc 的最大值达到 5.10 × 104 A·cm-2 (4.2 K, 5 T)。结合物相分析和显微组织观察表明，低温烧结后Sn进入Nb3Al的A15晶体结构形成Nb3(Al1-xSnx)相。此外，Sn掺杂改善了晶粒连通性并细化了Nb3Al的晶粒尺寸，这是Sn掺杂样品中Jc增强的主要原因。