A number of U-shaped K2NiF4-type oxide hollow fiber membranes based on (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+delta (PLNCG) were successfully prepared by a phase inversion spinning process. The PLNCG hollow fiber membranes were then used to investigate the effect of CO2 concentration in both the sweep gas and the feed air on the oxygen permeation flux. With pure CO2 as the sweep gas and even 10% CO2 in the feed air, a steady oxygen permeation flux of 0.9 mL/min center dot cm2 (STP) is obtained at 975 degrees C during 310 h, and no decline of the oxygen permeation flux is observed. XRD, SEM and EDS characterizations show the spent membrane still maintains the intact microstructure and perfect K2NiF4-type phase structure without carbonate, which indicates that the U-shaped PLNCG hollow fiber membrane is a very stable membrane under CO2 atmosphere and has great potential for the practical application in oxyfuel techniques for CO2 capture and storage.(c) 2011 American Institute of Chemical Engineers AIChE J, 2012