Characteristics of the annealed state of yttria and scandia stabilized zirconia have been investigated using molecular dynamics simulations. A genetic algorithm was used to find the minimal energy configuration of dopant ions to simulate the effects of annealing for compositions of 8 mol% Y2O3 in ZrO2, and compositions with 9, 10 and 11 mol% Sc2O3 with, respectively, 2, 1 and 0 mol% Y2O3 in ZrO2. Conductivity and diffusion coefficients were calculated in each case, and it was discovered that the conductivity increased when the dopant ions were located distan to each other, and the number of first neighbor dopant-dopan pairs were reduced. Furthermore, the Haven ratio was calculated to be on the order of 0.9 for the 11 mol% doped specimens, but substantially lower for the 8 mol% yttria in zirconia specimens.
Supercell images of annealed (left) and randomized (right) specimens of MSZ-2/9. Red spheres represent oxygen ions, while green spheres are zirconium, yellow are scandium and blue are yttrium.