Oxygen permeation of BSCF membrane with varying thickness and surface coating

The oxygen permeation of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) membranes was measured between 750 and 900 °C as a function of membrane thickness with or without La0.7Sr0.3CoO3 (LSC) coating layer under controlled PO2-gradientPO2-gradient (Air/He). In order to see the relative effects of bulk diffusion and surface-exchange kinetics, the thickness of membrane was varied from 0.5 to 2.0 mm. The oxygen-permeation flux at 900 °C increased with LSC coating from that of uncoated membrane. For example, it increased ∼1.8 times for 1 mm-thick BSCF membrane. The characteristic membrane thickness (LC) which divides the bulk-diffusion limit and surface-exchange kinetics limit was estimated using the modified Wagner equation. The LC values were 0.55 and 1.10 mm at 900 °C for the coated and uncoated BSCF membranes, respectively, and decreased with decreasing temperature.