Novel perovskite-type B-site Bi-doped BaBixCo0.2Fe0.8-xO3-delta (0.1 less than or equal to x less than or equal to 0.5) oxide membranes were exploited and synthesized. Oxygen permeation through these membranes was studied by the GC method using a high-temperature permeation cell. High permeation fluxes were observed. The permeation Aux of BaBi0.2Co0.2Fe0.6O3-delta membrane reached about 1 mi min(-1) cm(-2) under air/He gradients at 950 degrees C. The dependence of the permeation flux on thickness for BaBi0.3Co0.2Fe0.5O3-delta membrane was investigated in a wide temperature range from 600 degrees C to 950 degrees C. The permeation rate was controlled by surface exchange kinetics at lower temperatures. Bulk diffusion became partially rate-determining with rise in temperature. Oxygen temperature-programmed desorption (O-2-TPD) results showed very good oxygen adsorption and desorption reversibility of the materials. (C) 2000 Elsevier Science B.V. All rights reserved.