An architectural approach to the oxygen permeability of a La 0.6Sr 0.4Fe 0.9Ga 0.1O 3− δ perovskite membrane

Abstract

Multilayer membranes based on La 0.6Sr 0.4Fe 0.9Ga 0.1O 3− δ (LSFG) and La 0.6Sr 0.4Co 0.8Fe 0.2O 3− δ (LSCF) perovskite materials were fabricated to study the impact of membrane architecture on the oxygen permeability. Thick dense membrane and asymmetric membranes were shaped by tape casting and stacked to reach the desired architecture. Asymmetric membranes composed of a thin dense LSFG layer (120 μm) and a thick porous support layer (820 μm) of the same material were co-sintered to obtain crack-free and flat membranes. The use of large corn-starch particles (14 μm) as pore forming agent to the tape-casting slurries resulted in a connected porosity in the sintered support layer with low gas diffusion resistance. Oxygen permeation measurements in an air/argon gradient between 800 and 925 °C showed that the thickness of self-supported LSFG membranes was not the determining factor in the membrane performance for our testing conditions. A catalytic layer of La 0.6Sr 0.4Co 0.8Fe 0.2O 3− δ (LSCF), deposited on the membrane surfaces to catalyze the oxygen exchange reactions, leads to a significant increase of oxygen permeation rates. As the membrane thickness had no effect even if a catalyst coating was used, surface-exchange reactions were thought to be still limiting for the oxygen permeation fluxes. Thus, the improvement of surface activity of LSFG membrane was found to be a key point to reach higher oxygen permeation fluxes.