The crystal structure, oxygen permeation and stability of ZrO2-promoted SrCo0.4Fe0.6O3-delta (SCFZ) were compared with those of SrCo0.4Fe0.6O3-delta (SCF). X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis of SCFZ revealed that solubility of Zr into the SCF phase took place, resulting in a lattice expansion of SCF at high temperatures. SCFZ oxide showed enhanced structure stability compared to SCF without undergoing crystallographic phase transition when annealed in helium at high temperatures. The oxygen permeation experiments showed that long-term operation stability of the SCF membrane with addition of ZrO2 was greatly improved, the oxygen permeation flux, however, was slightly reduced probably due to the Zr dissolution in SCF. (C) 2003 Published by Elsevier Science B.V.