Defect interactions and ionic transport in scandia stabilized zirconia

Abstract

Classical molecular dynamics simulation has been used to study ionic transport in scandia-stabilized zirconia, as well as scandia and yttria-co-doped zirconia, as a function of temperature and composition. The oxygen diffusion coefficient shows a peak at a composition of 6 mol% Sc₂O₃. At 1125 K and higher temperatures, oxygen vacancies prefer to be second nearest neighbours to yttrium ions and first neighbours to scandium ions, because the defect interactions in scandia-stabilized zirconia are governed mainly by electrostatic effects. Oxygen migration between cation tetrahedra is impeded less effectively by Sc–Sc edges than by Y–Y edges. The formation of neutral dopant–anion vacancy clusters is favoured, in agreement with recent nuclear magnetic resonance observations.