Statistical thermodynamics of defects in ceria and perovskite based oxides

Abstract

The formation of oxygen vacancy defects in ceria and ceria zirconia solid solutions are analysed with a new methodology for modelling such systems based on the statistical mechanics of lattice configurations. Experimental thermogravimetric equilibrium data obtained for small non-stoichiometry measurements are combined with literature data to cover a large range of non-stoichiometry (CeO2-d , d = 0:001-0:32), temperature (1073 - 1773 K) and oxygen partial pressure (1 – 10^-13 bar). A dilute species model of defect clusters (Ce*VöCe*), obeying the law of mass action, was sufficient to describe the system over the whole range of conditions, leading to a simple analytical equation of state for the system. This offers new physical insight into the redox properties of ceria based materials, and the theoretical methods developed have also been successfully applied to model non-stoichiometry in perovskite based oxides.