Breakdown Phenomena of Anodic Oxide Films on Titanium

Abstract

Voltammogram and impedance measurements were applied for analysing the change in electronic property of the anodic oxide film formed on titanium in neutral borate solution with the electrolytic breakdown at anodic potentials higher than the breakdown potential of 7.5V. Anodic current histerisys was observed between the potential sweeps toward negative and positive directions for the film after the breakdown. The histerisys disappeared when the electrode was held at potentials lower than the breakdown potential. From analysis of the current histrisys it is suggested that high valency oxide such as TiO₃ or high valency state such as Ti⁵⁺ or Ti⁶⁺ are formed in the film at the breakdown. From the change of the Mott-Schottky plot with oxidation potential and period, it is estimated that the donor density in the oxide film increases after breakdown.