Computational Modeling Study of Bulk and Surface of Yttria-Stabilized Cubic Zirconia

Interatomic potential simulation techniques have been applied to both the bulk and surfaces of yttrium-stabilized cubic zirconia (YSZ). In the Mott−Littleton bulk calculations representing the infinitely dilute system, the yttrium dopants tend to exist as a pair with two yttriums close to each other and preferentially occupying the next-nearest neighbor (NNN) sites to the oxygen vacancy. However, the energy of the YSZ system as well as the configuration of defect cluster depends on the dopant concentration level. The calculated lattice energy for supercell models linearly increases with yttria content. At around 10% mol Y 2 O 3, the simulations indicate the existence of two stable cubiclike phases differencing in term of the detached arrangement of oxygen ions. Surface-energy calculations confirm the dominance of the (111) surface in c-ZrO 2 and YSZ. The yttrium solution energy at the surface has been estimated as a function of the Y dopant-vacancy cluster depth. The calculations demonstrate that for yttrium segregation to the top layers of the (111) surface. However, there is no evidence for strong segregation to the (110) surface.