Surface modification of La0.3Sr0.7C0O3-delta ceramic membranes

The dependence of oxygen permeability of dense La0.3Sr0.7CoO3-delta ceramic s on membrane thickness indicates significant surface exchange limitations to the permeation fluxes, which suggests a possibility to increase membrane performance by surface activation. The cobaltite membranes with various po rous layers applied onto the permeate-side surface were tested at 850-1120 K, Silver-modified La0.3Sr0.7CoO3-delta membranes showed enhanced permeatio n at temperatures above 950 K; deposition of porous layers of PrOx and Pr0. 7Sr0.3CoO3-delta had no positive effect. The maximum oxygen permeability at . These results 850-1120 K was observed in the case of porous La0.3Sr0.7CoO 3-delta layers with surface density about 10 mg cm(-2) suggest that the sur face exchange of lanthanum-strontium cobaltite membranes under an oxygen ch emical potential gradient is limited by both oxygen sorption at the surface and ion diffusion through the surface oxide layers. Oxygen permeability of La0.3Sr0.7CoO3-delta ceramics was found to increase with increasing grain size due to decreasing grain-boundary resistance to ionic transport. (C) 20 02 Elsevier Science B.V. All rights reserved.