Ceramic samples of CaTi0.8Fe0.2O3−δ were obtained from mechanically activated mixtures of TiO2, Fe2O3 and CaCO3 sintered at 1150C for 2h. The ceramics were dense with sub-micrometric grains with sizes in the order of 100–200nm and 400–600nm. X-ray diffraction analysis revealed a single perovskite phase structure indicating a high level of homogeneity, which was confirmed by transmission electron microscopy. The O permeability through these samples, measured in the range 700–950C, was about 50% lower than for ceramics with considerably larger grains, close to 10μm. The permeability increased linearly with the increase of the grain size in the range from ≈200nm to ≈10μm. Observations by results suggested that the grain boundaries have a negative impact on the high temperature ionic transport properties of CaTi0.8Fe0.2O3−δ ceramics.

Grain Size Effects on Oxygen Permeation in Sub-Micrometric CaTi0.8Fe0.2O3-δ Ceramics Obtained by Mechanical Activation. A.L.Shaula, R.O.Fuentes, F.M.Figueiredo, V.V.Kharton, F.M.B.Marques, J.R.Frade: Journal of the European Ceramic Society, 2005, 25[12], 2613-6