This study reports results for the morphology, crystal structure and critical parameters of Sm2O3-doped MgB2 wires with low and high initial filling densities. The transmission electron microscope (TEM) images were done for the longitudinal section of MgB2 wires. The results show that the Sm2O3 admixture significantly changes the morphology of the MgB2 material, accelerates the formation of the MgB2 phase, does not form rectangular MgB2 crystallites, does not leave pure Mg, and forms Sm2O3 areas of 10 nm and 20 nm. The effects of Sm2O3 addition on MgB2 formation in superconducting wires were revealed in detail in this study. Additionally, Sm2O3 causes the formation of point pinning regions that significantly increase the critical transport current density at the temperature range from 15 K to 30 K. The TEM images point out that rectangular MgB2 crystallites are formed in undoped MgB2 wires, which have not been previously reported. XRPD results showed that short-term heating allowed obtaining a larger amount of MgB2 phase for the MgB2 wire with high initial filling density. On the other hand, long heating time and high initial density slow down the creation of MgB2 phase when the Mg is in the solid state.

中文翻译：

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透射电子显微镜研究了 Sm2O3 掺杂剂对 MgB2 线结构、形貌和输运临界电流密度的影响


本研究报告了低初始填充密度和高初始填充密度的 Sm2O3 掺杂 MgB2 线的形态、晶体结构和关键参数的结果。透射电子显微镜 （TEM） 图像对 MgB2 线的纵截面进行了处理。结果表明，Sm2O3 外混物显著改变了 MgB2 材料的形貌，加速了 MgB2 相的形成，不形成矩形 MgB2 微晶，不留下纯 Mg，形成 10 nm 和 20 nm 的 Sm2O3 区域。本研究详细揭示了 Sm2O3 添加对超导线中 MgB2 形成的影响。此外，Sm2O3 会形成点固定区域，从而在 15 K 至 30 K 的温度范围内显著增加临界传输电流密度。TEM 图像指出，矩形 MgB2 微晶是在未掺杂的 MgB2 丝中形成的，这在以前没有报道过。XRPD 结果表明，短期加热允许为具有高初始填充密度的 MgB2 线获得更大量的 MgB2 相。另一方面，当 Mg 处于固态时，较长的加热时间和较高的初始密度会减慢 MgB2 相的产生。