STUDY OF OXYGEN VACANCY DIFFUSION IN YTTRIA-DOPED CERIA AND YTTRIA-STABILIZED ZIRCONIA BY STATISTICAL MOMENT METHOD

Oxygen vacancy diffusion in yttria-doped ceria (YDC) and yttria-stabilized zirconia(YSZ) are investigated using statistical moment method, including the anharmonicity effects of thermal lattice vibrations. The expressions of oxygen vacancy-dopant association energy and oxygen vacancy migration energy are derived in an explicit form. Calculation of the vacancy migration energy enable us to evaluate the important role of dopant cation on the oxygen vacancydiffusion. The dependences of the vacancy activation energies and diffusion coefficients in YDC and YSZ systems on dopant concentration are also discussed in detail. The calculated results are in good agreement with the other theoretical and experimental results.

Ionic Conductivity and Coordination Number of Cations in Ce1-xYxO2-x/2

Yttria doped ceria display higher ionic conductivity and stabilized phase which possess more advantage for solid oxide fuel cells. By using molecular dynamics simulation, the lattice parameter and oxygen conductivity of Ce1-xYxO2-x/2 (x = 0 - 0.65) at 1273 k have been investigated. Lattice parameters and ionic conductivity both increase with yttria doping while x < 0.15 but over doping of yttria lead to a decreasing trend on them. It is suggested that the closing distance of cation-anion is responsible for this decreasing. The coordination numbers of cations were also analyzed. The results showed that the vacancies prefer to locate near Y ions and vacancy ordering is independent with vacancy content.