Reducing anisotropic effects on oxygen separation performance of K2NiF4-type membranes by adjusting grain size

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)(1.9)Ni0.74Cu0.21Ga0.05O4+delta ((PL)(1.9)NCG) dense membranes, with a grain size of 8.2-166.4 mu m2, were prepared by adjusting the sintering conditions. The oxygen permeation fluxes through the (PL)(1.9)NCG 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 mu m(2), followed by an increase when the grain size exceeded the critical value (62.1 mu m(2)). As the structure, density, and surface exchange rates of the (PL)(1.9)NCG 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.

Automated summary

This study prepared a series of dense membranes of K2NiF4-type materials by adjusting grain size, revealing a unique relationship curve between oxygen permeation flux and grain size. It further demonstrated that grain size plays a significant role in influencing the oxygen permeability of membranes.