The poor reproducibility of intergrain critical current density J c in Fe-based superconductors is often believed to result from uncontrolled grain boundary (GB) connectivity degraded by extrinsic factors such as the local or global impurity concentration or GB porosity or cracks. Earlier we found that Ba and K can appear as oxide impurities at GBs, along with GB-wetting FeAs. In this study, we evaluated how the sample preparation environment and purity of the starting materials influence the polycrystalline J c in K-doped BaFe 2 As 2 (Ba122) bulks. Using a high-performance glovebox, the oxygen and water levels were significantly reduced, eliminating traces of FeAs. Oxide impurities and Ba (or K) segregation associated with oxygen in the starting materials were significantly reduced by using high purity starting materials. This combination essentially doubled the best J c (4.2 K) values to 2.3 × 10 5

中文翻译：

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消除K掺杂BaFe 2 As 2多晶体中氧化物杂质偏析的合成路线及其对晶粒间连接性的影响

通常认为，铁基超导体中的晶间临界电流密度J c的可复制性差，是由于外部因素（例如局部或整体杂质浓度或GB孔隙率或裂纹）导致的不受控制的晶界（GB）连接性降低所致。早先我们发现，Ba和K以及GB浸湿的FeAs都可以作为GB上的氧化物杂质出现。在这项研究中，我们评估了样品制备环境和起始原料的纯度如何影响K掺杂BaFe 2 As 2（Ba122）块体中的多晶J c。使用高性能手套箱，氧气和水的含量大大降低，消除了微量的FeAs。通过使用高纯度起始原料，可以显着减少起始杂质中的氧化物杂质和与氧相关的Ba（或K）偏析。