Changes in electrochemical properties of the anodic oxide film formed on titanium during potential sweep

Changes in electronic properties of the anodic oxide films formed on titanium in weakly alkaline borate solution were investigated by using impedance measurements. Analysis of the cyclic voltammogram and capacitance during the cyclic potential sweep suggested that the outer part of the anodic oxide film was converted. from an n-type semiconductor to a dielectric above 3 V, and converted to an n-type semiconductor again below 0.5 V. This phenomenon seems to be related to the dissociation of bound water in the film due to very high electric field applied to the oxide film. Formation of OH in the film may compensate the positive charge of the donor states and form Ti peroxides such as TiO3. These compounds are reduced below 0.5 V to show a characteristic cathode current peak. (C) 2001 Elsevier Science Ltd. All rights reserved.