Dilatometry and high-temperature X-ray diffractometry study of La0.6Sr0.4Ti0.1Fe0.9O3 − δ and La0.6Sr0.4Ti0.3Fe0.7O3 − δ oxygen-permeable membranes

The thermal expansion behavior of La0.6Sr0.4Ti1 − xFexO3 − δ (x = 0.7 and 0.9) was investigated by dilatometry and in situ powder X-ray diffractometry at 25 and 1000 °C under controlled oxygen partial pressures in air and at reducing atmosphere, PO2 = 0.21 and 1 × 10− 20 atm, respectively. The sintered samples of x = 0.7 and 0.9 showed positive thermal expansions, i.e., 12.4 and 14.4 × 10− 6 K− 1, respectively, in air up to 1000 °C, and also larger expansions at lower partial oxygen pressures, with a linear thermal expansion ratio factor of 0.10 and 0.40%. The change in the crystal lattice parameters analyzed by XRD Rietveld refinement showed that the crystal lattice volume increased with an increase in temperature and a decrease PO2. The linear thermal expansion rates estimated from volume change of the XRD data for the oxides of x = 0.7 and 0.9, were 0.13 and 0.27%, which corresponds to those of estimated from the dilatometry.