Cation doping and oxygen diffusion in zirconia: a combined atomistic simulation and molecular dynamics study

Computer simulation techniques have been used to investigate the defect and transport properties of the zirconia (ZrO2) oxygen-ion conductor. First, a wide variety of low-valent metal ions are substituted into zirconia, and the energetics of solution investigated. Favourable dopants (on energetic rounds) have been calculated and include CaO, Y2O3, Gd2O3, and Sc2O3 in agreement with observation. Dopant-vacancy clusters are also examined with the results revealing trends with dopant ion size and significant local atomic relaxation. These simulations are extended to encompass the topical area of Nb/Y co-doping in zirconia. Oxygen ion diffusion in yttria-stabilised zirconia is studied by application of molecular dynamics (MD) techniques; our results support models in which diffusion is mediated by oxygen vacancies, with calculated diffusion coefficients and activation energies in accord with tracer diffusion studies.