Influence of structural disorder on the dynamics of mobile oxygen ions in Dy2(Ti1−yZry)2O7

We report on the influence of structural disorder on the oxide-ion conductivity of Dy2(Ti1−yZry)2O7 (y = 0.55 and 0.90). A significant disorder is induced by mechanical milling synthesis of the samples, and, depending on the Zr/Ti, a partial and progressive structural ordering can be achieved by subsequent annealing at temperatures between 800 and 1500 °C. Ionic conductivity is relatively high for both compositions (up to 10−4 S/cm at 900 K), and the activation energies for dc conductivity (in the range 1.02–1.32 eV) are found to be larger in samples with more structural disorder. This result is quantitatively explained, by using Ngai’s coupling model, in terms of the enhancement of interactions between mobile oxygen vacancies in a more disordered structure.