Oxygen permeation through La0.4Sr0.6Co0.2Fe0.8O3-delta membrane

Dense La0.4Sr0.6Co0.2Fe0.8O3-delta oxygen-permeable membranes of different thickness were prepared by solid-state reaction. The oxygen flux facilitate d by an oxygen partial pressure difference across the oxide membrane was me asured at elevated temperatures. It is revealed that oxygen permeation flux is entirely controlled by the transport of oxide ions in the bulk of the m embrane in the thickness range of 1.25-2.46 mm. When the thickness is decre ased to 0.62 mm, it becomes jointly controlled by the oxygen exchange acros s the gas and solid interfaces. An electrochemical approach is adopted to a nalyze the thickness dependence of the oxygen flux. It is shown that the in terfacial process is more sensitive to the change of temperature, as eviden ced by the larger activation energy for the surface oxygen exchange (188.2 +/- 2.2 kJ mol(-l)), than that for the bulk transport (93.7 +/- 1.7 kJ mol( -l)).