Defect Chemistry of Singly and Doubly Doped Ceria: Correlation between Ion Transport and Energetics |
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| Authors: | Dr Salih Buyukkilic Prof Sangtae Kim Prof Alexandra Navrotsky |
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| Affiliation: | 1. Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (USA);2. Peter A. Rock Thermochemistry Laboratory and NEAT ORU University of California, Davis, CA 95616 (USA) |
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| Abstract: | Earlier studies have shown a strong correlation between the enthalpy of formation, ΔHf,ox, and the ionic conductivity, σi, near room temperature in doped ceria systems, which are promising solid electrolytes for intermediate‐temperature solid oxide fuel cells (IT‐SOFCs). The present work demonstrates that this correlation holds at the operating temperature of IT‐SOFCs, 600–700 °C. Solid solutions of Ce1?xNdxO2?0.5x, Ce1?xSmxO2?0.5x, and Ce1?xSm0.5xNd0.5xO2?0.5x are studied. The ΔHf,ox at 702 °C is determined by considering the excess heat content between 25 and 702 °C combined with the value of ΔHf,ox at 25 °C. Both σi and ΔHf,ox show maxima at x=0.15 and 0.20 for the singly and doubly doped ceria, respectively, suggesting that the number of mobile oxygen vacancies in these solid solutions reaches a maximum near those compositions. An increase in temperature results in a shift of the maximum in both ΔHf,ox and σi towards higher concentrations. This shift results from a gradual increase in dissociation of the defect associates. |
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| Keywords: | ceria doping ionic conductivity materials science solid solutions |
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