两步法合成BaK122前驱体的相变及反应动力学

IF 1.6 4区物理与天体物理 Q3 PHYSICS, CONDENSED MATTER

The European Physical Journal B Pub Date : 2025-04-29 DOI:10.1140/epjb/s10051-025-00927-0

Xinyuan Liu, Xianping Zhang, Chiheng Dong, Minghui Tang, Dongliang Wang, Yanwei Ma

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引用次数: 0

摘要

122型铁基超导体由于其在高场应用中的潜力而引起了相当大的兴趣。采用两步法制备BaK122前驱体粉末，提高了线材和胶带的超导性能。然而，杂质对提高临界电流密度构成了巨大的挑战，而其根本原因仍然是一个悬而未决的问题。本文研究了两步前驱体的相形成过程。550℃烧结后，大量生成砷化铁和KFe2As2。当烧结温度提高到700℃时，样品的超导性能得到明显改善。然而，K和Ba元素在122相中的分布仍然不均匀。850℃下烧结的样品，杂质几乎被消除，形成了高纯度的Ba0.6K0.4Fe2As2。各放热过程的反应机理均符合Avrami-Erofeev方程，表示为G(α) =[−ln(1-α)]1/n，对应于成核和晶体生长模型。基于以上结果，我们总结了二步法BaK122前驱体的相形成过程，并提出了杂质的形成机理。该研究为优化烧结工艺和提高BaK122前驱体的纯度提供了有价值的见解。图形抽象

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Phase transformation and reaction kinetics of BaK122 precursor synthesized via a two-step method

122-Type iron-based superconductors have gained considerable interest due to their potential for high-field applications. A two-step method for preparing BaK122 precursor powders is shown to enhance the superconducting performance of wires and tapes. However, impurities pose formidable challenges to enhancing critical current density, while their underlying causes remain an open question. In this work, the phase formation process of the two-step precursors was investigated. After sintering at 550 °C, iron arsenides and KFe₂As₂ are generated in large quantities. The superconducting properties of the sample improve significantly when the sintering temperature is increased to 700 °C. However, the distribution of K and Ba elements in the 122-phase remains inhomogeneous. For the samples sintered at 850 °C, impurities are almost eliminated, resulting in the formation of high-purity Ba_0.6K_0.4Fe₂As₂. The reaction mechanisms for each exothermic process follow the Avrami-Erofeev equation and are expressed as G(α) = [− ln(1-α)]^1/n, which corresponds to the nucleation and crystal growth model. Based on the above results, we summarize the phase formation process of the two-step BaK122 precursor and propose a formation mechanism for the impurities. This study provides valuable insights into optimizing the sintering process and improving the purity of BaK122 precursors.