Charge transfer at oxygen/zirconia interface at elevated temperatures Part 4: Work function v. defect chemistry

The present work considers the physical meaning of the work function of zirconia at elevated temperatures, corresponding to gas/solid equilibrium, as well as changes in work function as a result of surface reactions such as oxidation and reduction. The relationship between changes in work function and the oxygen partial pressure of both undoped zirconia and yttria-stabilised zirconia (YSZ) is considered in terms of the defect disorder of the outermost surface layer. Experimental work function data indicate that the surface properties of zirconia and its solid solutions are entirely different from those of the bulk phase. These differences are considered in terms of the functional properties of YSZ. The importance of work function measurements for the elucidation of surface semiconducting properties of metal oxides is discussed.