Dopant Clustering and Correlated Oxygen Migration in Conditionally Stabilized Zirconia Electrolytes

Abstract

Molecular dynamics (MD) simulation of yttria/scandiastabilized zirconia (SSZ) with variably distributed Y/Sc dopant ions shows that energy is minimized when the dopants are uniformly spread apart, provided that the lattice maintains cubic fluorite symmetry. In contrast, highly clustered dopants are found to destabilize the cubic phase due to the presence of large regions of dopantfree zirconia. Computed oxygen diffusion coefficients and conductivity values consistently show that the Haven ratio is always less than one, indicating that correlation effects influence the motion of oxygen ions and vacancies. In addition, it is seen that the conductivity of crystals with noncubic symmetry is markedly anisotropic.