The superionic conduction of O ions in 10mol% ytterbia-stabilized zirconia at various temperatures was studied by using molecular dynamics simulations. Although the discrete hopping of one or two O ions began at about 675K, the onset of superionic conduction occurred at about 1200K; where almost all of the O ions participated in the hopping process. The activation energy for O ion diffusion was found to be 53.25kJ/mol. At this temperature and above, the O ionic conductivity exceeded 0.1S/cm; thus confirming superionic conduction in this material. For 675K < T < 1200K, the material acted as a normal ionic conductor. The ionic conductivity values, obtained using the simulation, compared well with experimental results. However, the activation energy for O-ion conduction, found from the Arrhenius plot of the simulation, was equal to 52.71kJ/mol. This was 35% less than experimental value. The radial distribution functions showed that there was no sharp structural phase transition and no O-ion sub-lattice melting in this material at the superionic transition. However, a reduction in, broadening and shifting of the peaks in the radial distribution function for all ionic pairs, at higher temperatures, indicated a volume expansion of the crystal.

Molecular Dynamics Simulations of Oxygen Ion Diffusion and Superionic Conduction in Ytterbia-Stabilized Zirconia. T.P.Perumal, V.Sridhar, K.P.N.Murthy, K.S.Easwarakumar, S.Ramasamy: Computational Materials Science, 2007, 38[4], 865-72