Nanopowdered Ce 1−x Yb x O 2−ı solid solutions (0 ≤ x ≤ 0.2) were synthesized by a self-propagating room temperature synthesis. XRD and SEM were used to study the properties of these materials as well as the Yb solubility in CeO 2 lattice. Results showed that all the obtained powders were solid solutions with a fluoritetype crystal structure and with nanometric particle size. The average size of Ce 1−x Yb x O 2−ı particles was approximately 3 nm. Electrochemical impedance spectroscopy for the sintered pellets depicted that it was possible to separate R bulk and R gb in the temperature interval of 550-800 • C. The activation energy for the bulk conduction was 1.03 eV and for grain boundary conduction was 1.14 eV. Grain boundary resistivity dominates over the other resistivities. These measurements confirmed that Yb 3+-doped CeO 2 material had a potential as electrolyte for intermediate-temperature solid oxide fuel cell applications.

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Nanometric-sized strontium doped ceria powders were prepared by combustion glycine-nitrate procedure. Cerium nitrate and strontium nitrate were used as starting material whereas glycine is used as a fuel. The tailored composition was: Ce 1¹x Sr x O 2¹¤ with concentration "x" ranging from 0 to 0.15. The effect of dopant concentration and subsequent calcination on crystal stability and lattice parameter was studied. Results showed that the obtained powders were solid solutions with a fluorite-type crystal structure. The particle size was in the nanometric range (<15 nm). Calcination of as-prepared powders at 850°C caused the formation of secondary phase (SrCeO 3 ) in samples containing with fraction of Sr 2+ ions ²9 mol %. The solubility limit of Sr 2+ ions in ceria lattice was between 6 and 9 mol % at 850°C. The solid solution of 6 mol % Sr 2+ was stable even at temperature as high as 1550°C.

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