Dense perovskite materials exhibiting mixed ionic and electronic conductivity can be used as a membrane material for the production of oxygen of very high purity and in partial oxidation of methane to syngas in membrane reactors. They represent an attractive technology which is energy- and cost-efficient in comparison with conventional technologies in those fields. Currently, one of the most promising membrane materials is BaCo0.7Fe0.2Nb0.1O3-delta perovskite which possesses very high oxygen permeation flux. However, its stability is not satisfactorily high. In this work, Ba0.9Co0.7Fe0.2Nb0.1O3-delta perovskite was prepared by introducing A-site deficiency into BaCo0.7Fe0.2Nb0.1O3-delta and expected to enhance the stability and as well as the oxygen permeability. Under an air/helium oxygen gradient, the oxygen permeation flux of 1 mm thick Ba0.9Co0.7Fe0.2Nb0.1O3-delta membrane was 1.8 ml min(-1) cm(-2) at 875 degrees C, which is slightly higher than that of BaCo0.7Fe0.2Nb0.1O3-delta membrane under the similar condition. A 400 h durability test of Ba0.9Co0.7Fe0.2Nb0.1O3-delta membrane for POM reaction at 875 degrees C showed no degradation in the measured oxygen permeation flux and methane conversion, which indicated that Ba0.9Co0.7Fe0.2Nb0.1O3-delta had a significantly better stability than BaCo0.7Fe0.2Nb0.1O3-delta and could be a promising material for oxygen generator. (c) 2012 Elsevier B.V. All rights reserved.