Studying on the Point-Defect-Conductive Property of the Semiconducting Anodic Oxide Films on Titanium

By using electrochemical measurement techniques and based on the point-defect model (PDM), this work studied the point-defect-conductive property of the n-type semiconducting anodic oxide film formed on titanium under steady-state condition within the passive potential region of ca. in solution. The point-defect transport property was characterized by the steady-state current density through the film and the diffusion coefficient of the point defects in the film. It was demonstrated that with the increase of the film formation potentials, (and ) show an exponentially dependent increase on the potential. This behavior of the oxide films formed on titanium is to some extent different from that of some other n-type anodic oxide films. The influence of potential on the changes in structure and crystallization of the oxide film on titanium was proposed to be taken as a reason for the potential-dependence of (and ) observed in this work. It was also shown that within the passive potential region most of any change in the applied potential does appear predominantly as a change in the potential drop within the oxide film (only of that drops across the film/solution interface). Additionally, a question about the values of the polarizability of the oxide film/solution interface used and estimated within the frames of the PDM was raised and discussed at the end of this paper.