A dense perovskite hollow fiber made of BaCoxFeyZrzO3-delta (BCFZ) was evaluated for the oxygen separation at low temperatures (400-500 degrees C). An oxygen permeation flux of 0.45 ml/min cm(2) was obtained at 500 degrees C, which is the first oxygen permeation data reported at such low temperature so far. A degradation of the oxygen permeation at 500 degrees C was observed, but the oxygen fluxes through the hollow fiber membrane can be regenerated by thermal treatment at 925 degrees C for 1 h in air. Energy-dispersive X-ray spectroscopy (EDXS) shows that a strong element segregation occurs in the membrane during operation at low temperature. (c) 2008 Elsevier B.V. All rights reserved.