OXYGEN PERMEATION OF LA0.3SR0.7COO3-DELTA

The oxygen permeability of dense La0.3Sr0.7CoO3-delta membranes has be en measured in the range 750-1100 degrees C under various oxygen parti al pressure gradients. A sweep gas method was employed. Results indica te that in the range of thickness 0.057-0.215 cm used in the present s tudy, the oxygen flux is predominantly controlled by bulk diffusion ac ross the membrane. The measured activation energy is 60 kJ mol(-1). By fitting the permeation data for various thicknesses to the transport equation obtained upon assuming linear kinetics for the surface exchan ge reactions and bulk ionic transport, we could derive the oxygen ioni c conductivity and the characteristic membrane thickness. The latter q uantity determines the transition from predominant control by diffusio n to that by surface exchange. The ionic conductivity is about 0.5 S c m(-1) at 1000 degrees C. The characteristic thickness is extrapolated at a value of about 80 mu m.