Oxygen diffusion in yttria stabilised zirconia - experimental results and molecular dynamics calculations

Bulk oxygen self-diffusion in yttria-stabilised zirconia (YSZ) was investigated using tracer diffusion experiments and molecular dynamics (MD) simulation as a function of the yttria content. Experimentally, O-18 tracer diffusion was measured as a function of temperature (650-1200 K) and yttria content (8-24 mol% Y2O3) using gas-phase exchange of the stable isotope O-18 and SIMS analysis. For a given temperature, the diffusivity was highest for YSZ containing 10 mol% yttria. The activation enthalpy of diffusion was 0.8 to 1.0 eV, independent of the yttria content. The diffusion process was simulated with molecular dynamics using the program DL_POLY and comparing different potential sets. The oxygen diffusion coefficient was found to be of similar magnitude to the experimental value, and also showed similar concentration dependence with a maximum for YSZ containing 10 mol% yttria. The calculated activation enthalpies of oxygen transport are close to the values observed experimentally.