The compounds of SrCo0.8Fe0.2O3-delta (SCF) doped with Mg2+, Ca2+, Sr2+, Ba2+, Ti4+ and Zr4+ are synthesized by conventional solid reaction. The phase stabilities and oxygen permeabilites of these synthesized oxides are investigated. It is found that the doping Mg2+, Ca2+, Sr2+ and Ba2+ totally dissolve into the SCF unit cell, while SrTiO3 and SrZrO3 phases form when SCF is doped with Ti4+ and Zr4+, respectively. A possible mechanism of the doping behavior is proposed to interpret the structure transformation of the SCF unit cell. Phase stability increases directly with the size of the doping ion when SCF is doped with the ions in the same group. However, the influence of the size of the doping ion on the oxygen permeation behavior is negligible for the membranes doped with the ions in the same group. (C) 2003 Elsevier B.V. All rights reserved.