Molecular dynamics simulations of oxygen ion diffusion in yttria-stabilized zirconia

Oxygen ion diffusion in yttria-stabilized zirconia (YSZ) is studied employing molecular dynamics simulation. Oxygen ions migrate mainly by nearest neighbour hopping amongst the tetrahedral lattice sites of zirconium ions. A linear relation between the mean square displacement and time is found, after the oxygen ions have moved over distances much larger than the characteristic distances of the underlying crystal structure. In this diffusive region, the bulk oxygen tracer diffusion coefficient is 2.21×10−6 cm2 s−1 at 1759 K and 3.53×10−6 cm2 s−1 at 2057 K. The ionic conductivity, calculated from the bulk oxygen tracer diffusion coefficient, matches well with the experimental values. For all the ion pairs in YSZ, we have calculated the radial distribution function. We find that the peak height is smaller at higher temperature, due to the volume expansion of the YSZ crystal.