Ion diffusion across/along symmetric tilt grain boundaries in yttria-stabilized zirconia investigated by molecular dynamics simulations

Abstract

Atomic arrangements around symmetric tilt grain boundaries (GBs) Σ3[110]/{111}, Σ9[110]/{221} and Σ11[110]/{113} in yttria-stabilized zirconia (YSZ) and influence of these GBs on oxygen ion diffusion were investigated by molecular dynamics (MD) simulations. The models including those GBs along which yttrium ions are segregated were used for simulations. The atomic arrangements obtained by MD simulations were consistent with the structure obtained by using advanced electron microscopy techniques. MD simulations predict that Σ11[110]/{113} GB reduce oxygen ion diffusion both across and along GB, while Σ9[110]/{221} GB does not give large influence on the diffusion. The origin of such difference can be explained systematically based on the variation of nearest neighbor OO distance which may change the probability of oxygen ion hopping from one site to another. The simulated results also predict the emergence of two-dimensional honeycomb-shaped path networks of oxygen ion diffusion along the cores of Σ3[110]/{111} symmetric tilt GB in YSZ. The unique honeycomb networks have the potential for enhancing the ion diffusion along GBs.