INTERFACIAL ELECTROSTATIC BEHAVIOR OF OXIDES - CORRELATIONS WITH STRUCTURAL AND SURFACE PARAMETERS OF THE PHASE

The electrochemical behaviour of aqueous suspensions of ZrO2 powders, either pure phase (monoclinic and tetragonal) or mixtures of polymorph s, was investigated. Surface charge and total capacitance vs. pH curve s, for the pure oxides, were regular showing different values of point s of zero charge and low inner layer capacitance values. The mixtures of the polymorphs presented atypical interfacial electrochemical featu res which were interpreted as due to patch wise heterogeneity. This la tter hypothesis was supported by XPS analyses of the powders which ind icated, in the case of the mixtures of the polymorphs, the presence of heterogeneity both in composition and in the acid-base character of t he surface sites.