The 1144 family of Iron Based Superconductors (IBSCs) is characterized by critical currents among the highest for single crystalline IBSCs. The synthesis of polycrystalline compounds is usually carried out through high temperature (T > 900 °C) processes. These methods, justified by a supposed thermodynamic instability of the 1144 phase at low temperature, are complicated by the presence of highly volatile elements and require fast heating and cooling steps. Here, it is shown how a High Energy Ball Milling (HEBM) treatment is effective to promote the reaction among the starting elements, thus favoring the synthesis of the 1144 phase at lower temperature. The evolution of the powders has been assessed for different milling times, observing the consumption of the starting reactants and the formation of crystalline pnictide phases. Different thermal treatments have been coupled to the HEBM treatment, allowing the study of the effect of time and temperature of the thermal step on the materials properties. It has been observed how the formation of the superconducting phase occurs on the HEBM samples at 500 °C and 600 °C. Critical temperatures comparable with data reported in the literature were obtained. Granularity phenomena and critical current density of sintered samples are highly dependent on the processing variables.

中文翻译：

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Ca/K 1144 型铁磷化物的机械化学辅助合成


1144 系列铁基超导体 (IBSC) 的特点是具有单晶 IBSC 中最高的临界电流。多晶化合物的合成通常通过高温（T > 900 °C）过程进行。这些方法以 1144 相在低温下的假定热力学不稳定性为依据，但由于高挥发性元素的存在而变得复杂，并且需要快速加热和冷却步骤。这里展示了高能球磨 (HEBM) 处理如何有效促进起始元素之间的反应，从而有利于在较低温度下合成 1144 相。评估了不同研磨时间下粉末的演变，观察起始反应物的消耗和结晶磷族元素相的形成。不同的热处理与 HEBM 处理相结合，可以研究热步骤的时间和温度对材料性能的影响。已经观察到在 500 °C 和 600 °C 的 HEBM 样品上超导相的形成是如何发生的。获得了与文献中报道的数据相当的临界温度。烧结样品的粒度现象和临界电流密度高度依赖于加工变量。