Processing and oxygen permeability of asymmetric ferrite-based ceramic membranes

In order to assess membrane architecture-related effects on the oxygen transport through ferrite-based mixed conductors, a series of planar ceramic membranes with dense layers made of the dual-phase (SrFeO3 − δ)0.7(SrAl2O4)0.3 composite were appraised at 1023–1223 K under oxidizing conditions. The asymmetric membranes with porous La0.5Sr0.5FeO3 − δ and (SrFeO3 − δ)0.7(SrAl2O4)0.3 supports were fabricated by a two-stage compaction procedure using various pore-forming additives and sintering at 1623–1723 K. Analysis of the oxygen permeation fluxes through model symmetric membranes showed significant limiting role of the composite surface oxygen exchange. At temperatures above 1173 K, a substantially improved performance was observed for asymmetric self-supported composite membranes with the dense layer thickness of 0.12 mm, surface-modified with (SrFeO3 − δ)0.7(SrAl2O4)0.3–Pt mixture. At 1023–1173 K, higher oxygen fluxes were achieved using perovskite-type La0.5Sr0.5FeO3 − δ as the porous support material.