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As a promising electrolyte material for intermediate-temperature solid oxide fuel cells operated at a temperature of

Inhomogeneous microstructures, including nanosized domains and nanoprecipitates, were observed in sintered samples of holmium-doped ceria. The formation of such microstructural inhomogeneity is related to the segregation of dopant cations and can be enhanced by increasing doping concentration and sintering temperature. Through examination of the relationship between the microstructures and electrical properties, it was found that the inhomogeneity can have negative impacts on ionic conduction, which could be explained in terms of the interaction between the oxygen vacancies and the segregated dopant cations. (C) 2007 The Electrochemical Society.

The ionic conductivities and microstructures of Ce1-xYbxO2-x/2 ( x = 0.10, 0.15, 0.20, and 0.25 ) with average grain sizes in a range of 0.2 - 3.7 mu m were studied systematically. Nanosized domains were confirmed through detailed studies of transmission electron microscopy. The relationships of the domains, doping concentration, and grain size were determined, and their effects on the ionic conductivities were examined. It was concluded that the domains were formed via the segregation of Yb cations so that they could trap the oxygen vacancies and lower the conductivity. Furthermore, the development of the domains, which depends on the doping concentration and grain size, can affect the doping concentration and grain-size dependencies of the conductivity. (c) 2006 The Electrochemical Society.