Further performance improvement of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ perovskite membranes for air separation

Perovskite Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) is a promising mixed conducting ceramic membrane material for air separation. In this work, BSCF powder was synthesized by a modified Pechini sol-gel technique at relatively lower temperature. The O₂ permeation through a series of BSCF membranes has been tested at different temperatures and various O₂ partial pressure gradients. Theoretical investigation indicated that bulk diffusion and the O₂ exchange reactions on membrane surfaces jointly controlled the O₂ permeation through BSCF membranes with thickness of between 1.1 and 0.75 mm. To further improve the O₂ fluxes, effective efforts are made on membrane thickness reduction and surface modification by spraying porous BSCF layers on both surfaces. When the membrane thickness was reduced from 0.75 to 0.40 mm, the O₂ fluxes were increased by 20-60% depending on the operating conditions. The surface modification further improved the O₂ flux by another 20-40%. The high O₂ fluxes achieved in this work are quite encouraging with a maximum value reaching 6.0 mL min^-1 cm^-2 at 900 °C.