Effect of the Σ 5 ( 310 ) / [ 001 ] tilt grain boundary on oxygen-ion movement in yttria-stabilized zirconia: Insights from molecular dynamics

We present a new methodology for investigating the combined effect of the Σ 5 ( 310 ) / [ 001 ] symmetric tilt grain boundary (GB) and the local cation environment in polycrystalline yttria stabilized zirconia (YSZ) on two important quantities that determine the ionic conductivity, namely, (i) the local hopping rate of O ²⁻ ion and (ii) the probability of O ^2--ion -vacancy pairs within the YSZ structure. How these quantities vary with distance to the GB core are estimated for the first time using waiting time distributions associated with O ²⁻ ion hop events in molecular dynamics simulations. We conclude that indeed fewer hop events occur in the presence of a GB. However, the GB effect can be felt at a far greater distance than previously believed. Most importantly, interactions between the O ²⁻ ions, nearby cations and the GB results in a hopping behavior that is different from one observed in single-crystal YSZ. Anisotropy in O ²⁻ ion movement in the vicinity of the GB is also studied. These results and the use of our novel technique have a direct implication on the development of improved models for ionic conduction in solid state electrolytes.