Journal
CHEMISTRY OF MATERIALS
Volume 24, Issue 1, Pages 222-229Publisher
AMER CHEMICAL SOC
DOI: 10.1021/cm2031152
Keywords
reverse Monte Carlo (RMC); molecular dynamics (MD); oxygen vacancy ordering; cation interactions; doped ceria (CeO2); SOFC electrolytes
Funding
- EU
- Government of Ireland
- Science Foundation Ireland [08/RFP/MTR1044, 09/RFP/MTR2274]
- Science Foundation Ireland (SFI) [08/RFP/MTR1044, 09/RFP/MTR2274] Funding Source: Science Foundation Ireland (SFI)
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The defect structure and ionic diffusion processes within the anion-deficient, fluorite structured system Ce1-xYxO2-x/2 have been investigated at high temperatures (873 K-1073 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-ion 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-vacancy 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 property relationships within anion-deficient fluorite structured oxides are briefly discussed, with reference to complementary studies of yttria and/or scandia doped zirconia published previously.
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