Atomistic modeling study of surface effect on oxide ion diffusion in yttria-stabilized zirconia

Abstract

This paper reports the results of a molecular dynamics (MD) study of oxide ion diffusion in cubic yttria-stabilized zirconia (YSZ) using our recently developed interatomic potential [A.M. Iskandarov et al., J. Phys.: Condens. Matter 27, 015005 (2015)], which is based on the Tangney–Scandolo dipole model. We demonstrate that our potential can reproduce oxide ion conductivity in bulk YSZ with yttria concentrations varying from 2 to 14 mol%. We confirm the significant effect of free surfaces on oxygen diffusion by direct MD calculations at elevated temperatures and nudged elastic band analyses. It was found that oxygen vacancies tend to migrate from the (111) surface and locate in the bulk region, suppressing local oxide ion diffusion at the surface. In contrast, higher oxygen vacancy concentration and activation of oxide ion jumps along the 〈110〉 direction facilitate oxygen diffusion at the (110) surface. The MD results for the (110) surface are supported by density functional theory calculations.