Defect interactions and ionic transport in scandia stabilized zirconia

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% Sc(2)O(3). 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.