Passivity of titanium, part IV: reversible oxygen vacancy generation/annihilation

Abstract

A simplified Point Defect Model incorporating reversible oxygen vacancy generation/annihilation at the metal/film interface has been used to investigate the impedance of anodized titanium in 0.5 M H2SO4, the oxygen vacancy profile in the anodic titanium oxide film, and the surface oxygen vacancy concentration. This simplified Point Defect Model (PDM), which considers the oxygen vacancy as the only point defect in the film, successfully accounts for the impedance of anodized titanium over the potential range explored. The results indicate that there is a thin region of the non-uniform oxygen vacancy concentration adjacent to the film/solution interface, which has an exponentially decreasing dopant ( $$ {V}_O^{\cdot \cdot } $$ ) concentration. The results of the investigation show that the surface oxygen vacancy concentration normalized to the bulk oxygen vacancy concentration is in the range of 0.05–0.15 and is essentially independent of potential.