At low concentrations, stabilizing yttria served to increase the oxygen diffusivity through the presence of corresponding oxygen vacancies required to maintain charge neutrality. At higher yttria concentrations, the diffusivity was impeded by the larger number of relatively high energy migration barriers associated with yttrium cations. There was also evidence that oxygen vacancies preferentially occupied nearest-neighbor sites around either dopant or Zr cations; further affecting vacancy diffusion. Ab initio calculations indicated that it was energetically favorable for oxygen vacancies to occupy nearest-neighbor sites adjacent to Y ions, and that the presence of vacancies near to either species of cation lowered the migration barriers. Kinetic Monte Carlo results from simulations incorporating this effect were compared with the results of simulations in which the effect was not present.

Kinetic Monte Carlo Investigation of the Effects of Vacancy Pairing on Oxygen Diffusivity in Yttria-Stabilized Zirconia. B.S.Good: Materials Research Society Symposium Proceedings, 2011, 1331, 1-6