Oxygen transport through dense perovskite-type La1-xSrxFeO3-δ membranes

Oxygen permeation measurements were performed on dense La1-xSrxFeO3-δ (r=0.1-0.4) membranes at 1273 K. The materials were investigated in air/He and air/He,CO,CO2 gradients. The fluxes increased with increasing Sr content and were strongly enhanced by the presence of CO, up to values of 25 mmol m-2 s-1. In air/He gradients the permeation is bulk controlled and can be modelled by Wagner theory incorporating a random point defect model. Oxygen vacancy diffusion coefficients were calculated to range between 5.6-8.6-10-6 cm2 s-1. In air/CO,CO2 gradients the permeation process appeared to be totally limited by the surface reaction rate. To account for this behaviour, models are proposed in which surface oxygen vacancies act as active surface sites.