Properties of CaTi1-xFexO3-δ ceramic membranes

CaCO3, TiO2 and Fe2O3 were mixed in the appropriate stoichiometric quantities and calcined at 1100degreesC for 10 It. These powder mixtures were uniaxially pressed and sintered at temperatures ranging from 1350 to 1500degreesC for 2 h in order to obtain dense disk-shaped samples with nominal CaTi1-xFexO3-delta (x = 0.05, 0.15, 0.20, 0.40 and 0.60) compositions. Dilatometry and in situ high temperature powder X-ray diffraction analysis showed a good agreement on the thermal expansion behaviour of these materials between room temperature and 1000degreesC. The estimated linear thermal expansion coefficient is close to 13 x 10(-6) K-1 and is little affected by composition. No evidence for surface carbonation was detected in the infrared spectra collected on samples previously annealed in CO2 atmospheres. The oxygen permeability measured at temperatures ranging from 750 to 1000degreesC goes through a sharp maximum for x = 0.20. This result is interpreted by structural differences related to change from disordered to ordered oxygen vacancies. The overall performance of CaTi0.80Fe0.20O3-delta is compared to other mixed conducting materials.