Preparation and Oxygen Permeation Properties of Highly Asymmetric La0.6Sr0.4Co0.2Fe0.8O3-α Perovskite Hollow-Fiber Membranes

La0.6Sr0.4Co0.2Fe0.8O3-alpha (LSCF) perovskite powders having a submicrometer size were synthesized by a sol-gel autocombustion method. From these powders, the gastight LSCF hollow-fiber membranes with a highly asymmetric structure comprising a dense layer of thickness ca. 88 mu m integrated with a porous substrate were fabricated in a single step through a phase inversion/sintering technique with a mixture of N-methyl-2-pyrrolidone (NMP) and water as internal coagulant. Oxygen permeation fluxes through the obtained hollow-fiber membranes were measured under air/He gradients at different temperatures. The results indicate that the highly asymmetric hollow-fiber membranes possess an oxygen permeation flux of 0.11-2.19 mL cm(-2) min(-1) in the temperature range of 650-1000 degrees C, which is 2.6-10.5 times higher than that of the sandwich-structured hollow-fiber membranes. Oxygen permeation in the hollow-fiber membranes is limited primarily by the surface exchange reactions at lower temperatures, but ionic bulk diffusion will have a rate-limiting effect at temperatures higher than 900 degrees C.