Grain size effects on oxygen permeation in submicrometric CaTi0.8Fe0.2O3-delta ceramics obtained by mechanical activation


Ceramic samples of CaTi0.8Fe0.2O3-delta were obtained from mechanically activated mixtures of TiO2, Fe2O3 and CaCO3 sintered at 1150 degrees C for 2 h. The ceramics are dense with submicrometric grains with sizes in the order of 100-200 nm and 400-600 nm. X-ray diffraction analysis revealed a single perovskite phase structure indicating a high level of homogeneity, which was confirmed by transmission electron microscopy. The oxygen permeability through these samples, measured in the range 700-950 degrees C, is about 50% lower than for ceramics with considerably larger grains, close to 10 mu m. The permeability increases linearly with the increase of the grain size in the range from approximate to 200 nm to approximate to 10 mu m. Observations by results suggest that the grain boundaries have a negative impact on the high temperature ionic transport properties of CaTi0.8Fe0.2O3-delta ceramics. (c) 2005 Elsevier Ltd. All rights reserved.



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Materials Science


Shaula, AL; Fuentes, RO; Figueiredo, FM; Kharton, VV; Marques, FMB; Frade, JR

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