Atomistic modeling of La3+ doping segregation effect on nanocrystalline yttria-stabilized zirconia

Abstract

The effect of La³⁺ doping on the structure and ionic conductivity change in nanocrystalline yttria-stabilized zirconia (YSZ) was studied using a combination of Monte Carlo and molecular dynamics simulations. The simulation revealed the segregation of La³⁺ at eight tilt grain boundary (GB) structures and predicted an average grain boundary (GB) energy decrease of 0.25 J m⁻², which is close to the experimental values reported in the literature. Cation stabilization was found to be the main reason for the GB energy decrease, and energy fluctuations near the grain boundary are smoothed out with La³⁺ segregation. Both dynamic and energetic analysis on the Σ13(510)/[001] GB structure revealed La³⁺ doping hinders O²⁻ diffusion in the GB region, where the diffusion coefficient monotonically decreases with increasing La³⁺ doping concentration. The effect was attributed to the increase in the site-dependent migration barriers for O²⁻ hopping caused by segregated La³⁺, which also leads to anisotropic diffusion at the GB.