The perovskite-type oxide SrCo0.8Fe0.2O3 δ (SCF), a highly oxygen-permeable material, is restricted for application in the membrane-integrated oxy-fuel combustion process by its low tolerance to CO2. In the present work, we found that the CO2 tolerance of SCF is improved by increasing the oxygen partial pressure in the CO2-containing gas. Long term oxygen permeation experiments, at 950 1C, show that mixing 5% of oxygen into the CO2 sweep gas effectively prevents degradation of the SCF membrane. X-ray photoelectron spectroscopy indicates that the increase in CO2 tolerance of SCF is caused by a decrease in basicity of the material with increasing oxygen partial pressure. Based on these experimental results, a modified oxy-fuel combustion process is proposed. Calculation of the required membrane area for operating a 50 MW coal-ired power plant showed that the modified process comprises a viable option.