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 ${\mathrm{Sc}}^{3+}$ and 9 at. % for ${\mathrm{Y}}^{3+}$, 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.

• Received 25 September 2017
• Revised 27 March 2018

DOI:https://doi.org/10.1103/PhysRevApplied.10.014032