U-shaped K2NiF4-type oxide hollow-fiber membranes based on (Pr0.9La0.1)(2)(Ni0.74Cu0.21Ga0.05)O4+delta (PLNCG) were successfully prepared through a phase-inversion spinning process. The effect of CO2 and SO2 on the oxygen permeation, phase structure and the microstructure of the material were investigated. In situ XRD patterns of PLNCG under air, Ar and CO2 atmosphere in the range from room temperature to 1000 degrees C were performed and indicate a good phase stability under oxidizing and reducing conditions as well as chemical stability against CO2. Effects of SO2 concentration in the sweep gas and the feed gas on the oxygen permeation flux through the PLNCG hollow-fiber membrane, as well as on membrane's microstructure were also investigated. Pr2O2SO4, La2O2SO4 and NiO formed after SO2 treatment and the material developed some porosity on the side exposed to SO2. The observations indicate that the PLNCG membrane is highly stable against CO2 but sensitive to SO2. (C) 2012 Elsevier B.V. All rights reserved.