In situ high temperature X-ray diffraction studies of mixed ionic and electronic conducting perovskite-type membranes

Phase structure and stability of three typical mixed ionic and electronic conducting perovskite-type membranes, SrCo0.8Fe0.2O3−δ (SCF), Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) and BaCo0.4Fe0.4Zr0.2O3−δ (BCFZ) were studied by in situ high temperature X-ray diffraction at temperatures from 303 to 1273 K and under different atmospheres (air, 2% O2 in Ar and pure Ar) at 1173 K. By analyzing their lattice parameters the thermal expansion coefficients (TECs) of BSCF, SCF and BCZF are obtained to be 11.5 × 10− 6 K− 1, 17.9 × 10− 6 K− 1 and 10.3 × 10− 6 K− 1, respectively. A relationship between phase stability and TEC was proposed: the higher is the TEC, the lower is the operation stability of the perovskite materials.