Oxygen Vacancy Ordering and the Conductivity Maximum in Y2O3-Doped CeO2

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• 作者：Mario Burbano ; Stefan T. Norberg ; Stephen Hull ; Sten G. Eriksson ; Dario Marrocchelli ; Paul A. Madden ; Graeme W. Watson
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：January 10, 2012
• 年：2012
• 卷：24
• 期：1
• 页码：222-229
• 全文大小：416K
• 年卷期：v.24,no.1(January 10, 2012)
• ISSN：1520-5002

文摘

The defect structure and ionic diffusion processes within the anion-deficient, fluorite structured system Ce_1鈥?i>xY_xO_2鈥?i>x/2 have been investigated at high temperatures (873 K鈥?073 K) as a function of dopant concentration, x, using a combination of neutron diffraction studies, impedance spectroscopy measurements, and molecular dynamics (MD) simulations using interionic potentials developed from ab initio calculations. Particular attention is paid to the short-range ion鈥搃on correlations, with no strong evidence that the anion vacancies prefer, at high temperature, to reside in the vicinity of either cationic species. However, the vacancy鈥搗acancy interactions play a more important role, with preferential ordering of vacancy pairs along the 111 directions, driven by their strong repulsion at closer distances, becoming dominant at high values of x. This effect explains the presence of a maximum in the ionic conductivity in the intermediate temperature range as a function of increasing x. The wider implications of these conclusions for understanding the structure鈥損roperty relationships within anion-deficient fluorite structured oxides are briefly discussed, with reference to complementary studies of yttria and/or scandia doped zirconia published previously.

Keywords:

reverse Monte Carlo (RMC); molecular dynamics (MD); oxygen vacancy ordering; cation interactions; doped ceria (CeO₂); SOFC electrolytes