Molecular dynamics simulations were used to calculate the ionic conductivity of zirconia samples with Y2O3 concentrations ranging from 5.9 to 12.5mol%. The calculated conductivity exhibited a maximum value at 8mol%Y2O3; in agreement with previously reported experimental data. In order to clarify the reason for the conductivity maximum, the position which was occupied by O vacancies was determined. It was found that O vacancies were trapped at the second-neighbour positions to the Y ions. It was also found that the number of O sites which trapped a vacancy increased with increasing Y2O3 concentration. Therefore, a balance between an increase in the number of vacancies and a decrease in vacancy mobility was concluded to be the reason for the maximum in ionic conductivity.

Molecular Dynamics Analysis of Ionic Conduction Mechanism in Yttria-Stabilized Zirconia. Y.Yamamura, S.Kawasaki, H.Sakai: Solid State Ionics, 1999, 126[1-2], 181-9