Abstract The microstructure of membranes (especially the grain size) has a considerable influence on their oxygen separation performance. Numerous studies focused on isotropic materials such as perovskites, while only a few investigated anisotropic K2NiF4-type materials due to their complex oxygen ion transport paths. In this work, a series of K2NiF4-type (Pr0.9La0.1)1.9Ni0.74Cu0.21Ga0.05O4+δ ((PL)1.9NCG) dense membranes, with a grain size of 8.2–166.4 μm2, were prepared by adjusting the sintering conditions. The oxygen permeation fluxes through the (PL)1.9NCG membranes displayed a unique concave curve as a function of the grain size, with an initial decrease when the grain size increased from 8.2–62.1 μm2, followed by an increase when the grain size exceeded the critical value (62.1 μm2). As the structure, density, and surface exchange rates of the (PL)1.9NCG membranes were found to alter slightly with the grain size, the differences in the oxygen permeability were deduced to be originating from the anisotropic bulk diffusion process. Therefore, adjusting the grain size is an effective strategy for enhancing the oxygen permeability of anisotropic membranes.

中文翻译：

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通过调节粒径降低各向异性对 K2NiF4 型膜氧分离性能的影响

摘要 膜的微观结构（尤其是粒径）对其氧分离性能有相当大的影响。许多研究都集中在钙钛矿等各向同性材料上，而由于其复杂的氧离子传输路径，只有少数研究了各向异性 K2NiF4 型材料。在这项工作中，通过以下方法制备了一系列 K2NiF4 型 (Pr0.9La0.1)1.9Ni0.74Cu0.21Ga0.05O4+δ ((PL)1.9NCG) 致密膜，粒径为 8.2-166.4 μm2调整烧结条件。通过 (PL)1.9NCG 膜的氧渗透通量显示出独特的凹曲线作为晶粒尺寸的函数，当晶粒尺寸从 8.2-62.1 μm2 增加时开始下降，当晶粒尺寸超过临界值 (62.1 μm2)。由于结构、密度、和 (PL)1.9NCG 膜的表面交换率被发现随晶粒尺寸而略有变化，透氧率的差异被推断出源于各向异性体扩散过程。因此，调整粒径是提高各向异性膜透氧性的有效策略。