A highly oxygen-permeable membrane was produced by substituting Zr for Fe through the solid-state reaction in the nominal La0.2Ba0.8Co0.8Fe0.2O3-delta composition. In the temperature range of 700-1000 degrees C, the La0.2Ba0.8Co0.8Fe0.2-xZrxO3-delta membrane with x = 0.05 had a remarkably high permeation flux because of the oxygen-vacancy-disordered structure of the membrane. For La0.2Ba0.8Co0.8Fe0.2O3-delta and La0.2Ba0.8Co0.8Fe0.175Zr0.025O3-delta, it was believed that the structure of the membranes changed from the oxide vacancy disordered to the ordered at approximately 920 degrees C. For La0.2Ba0.8Co0.8Fe0.15Zr0.05O3-delta, the change took place below 700 degrees C. (c) 2006 Elsevier B.V. All rights reserved.