Defect Interactions in the CeO2-ZrO2-Y2O3 Solid Solution

The solid solutions CeO2-ZrO2 and CeO2-ZrO2-Y2O3 are of interest for applications in industrial catalysis and automotive exhaust purification and possess high oxygen storage capacity. The reduction properties are greatly influenced by the interaction of defects in the ceria host lattice. The large number of different defects complicates the description of these materials. In this study, the interactions of defects in cerium oxide substituted with zirconium oxide and yttrium oxide were investigated, both for stoichiometric and nonstoichiometric composition, by means of density functional theory and Monte Carlo simulations. From the simulations, the impact of defect interactions on the energy of reduction was obtained. In agreement with experimental data, substitution with zirconium oxide leads to a strong decrease of the energy of reduction, which originated from the association between oxygen vacancies and zirconium ions. Detailed analysis of the calculated structures reveals pronounced local relaxation as the origin of the strong association.