Computational and Experimental Investigations of Defect Interaction and Ionic Conductivity in Doped Zirconia

Zirconia is a promising electrolyte material that has been widely used in solid-oxide fuel cells. In this paper, the effects of defect interaction on the ionic conductivity of scandia-and yttria-doped zirconia are systematically investigated by density-functional-theory calculations and experimental verification. We theoretically predict the doping concentrations of the tetragonal-to-cubic phase transition to be 18 at. % for Sc3+ and 9 at. % for Y3+, which are in reasonable agreement with the experimental values. Oxygen-vacancy-formation energies, oxygen-vacancy-dopant binding energies, and diffusion barriers are calculated to evaluate ionic conduction properties. Our calculated results show that the binding-energy variances of different defect configurations in scandia-doped zirconia are markedly lower than those in yttria-doped zirconia. Diffusion barriers are calculated using the saddle-point method, and the corresponding experiments are carried out to verify the diffusion-barrier results.