We report the results of our studies on oxygen permeability, phase stability, and chemical compatibility of a dual phase membrane consisting of A-site deficient mixed conducting perovskite, Sr0.95Fe05 Co0.5O3-delta (SFC), and an ionically conducting fluorite, Ce0.9Gd0.1O2-delta (CGO), with 1:1 volume ratio. The permeation rate of the SFC-CGO membrane with activated surface was found to be appreciably high (similar to 0.3 mlcm(-2)min(-1) at 850 degrees C). More importantly, the perovskite phase of SFC in the dual-phase membrane remained stable even under the conditions where the single-phase SFC membrane undergoes phase transformation. Furthermore the results of spatially resolved electron energy-loss spectroscopy (EELS) analysis indicated no sign of chemical reaction or intermixing between the two oxide phases during the membrane operation, which is often reported to occur in the similar types of dual-phase membranes. Therefore this SFC-CGO dual phase membrane may meet the requirements for the oxygen transport membrane (OTM) used in the oxy-fuel reactors. (C) 2014 Elsevier B.V. All rights reserved.