Oxygen vacancy ordering induced displacements of cations in yttria-stabilized zirconia

Using scanning transmission electron microscopy, we report direct observation of oxygen vacancy ordering induced atomic displacements of the cation sub-lattice in yttria-stabilized zirconia (YSZ). We find that the cation lattice adopts a zigzag configuration along the [100] direction with alternately narrow and wide lattice spacings equivalent of 0.85 and 1.15 times of the (200) inter-planar distance of the cubic YSZ. Using atomistic simulations, we show that the cation displacements are induced by the alternate presence of oxygen vacancies at the (1/4, 1/4, 1/4) and (1/4, 3/4, 1/4) sites of the unit cells in the [001] direction. The results demonstrate that significant enrichment of yttrium atoms can occur within individual YSZ grains in addition to the typical surface or grain boundary segregation of dopant atoms. (C) 2016 Author(s).