Abstract
The ESR spectra of anodized alumina films, which had been formed in various electrolytes, were studied and the oxide films were classified into the following two groups:
(1) Strong ESR spectrum
This type of film was obtained in organic acid electrolytes such as oxalic acid and NMF-boric acid system.
(2) Weak ESR spectrum
This type of film was obtained in electrolytes containing sulfur such as sulfuric and sulfamic acids.
When the films of Type (II), which had been formed in sulfuric acid, sulfamic acid, and sulfosalicylic acid+sulfuric acid were irradiated by γ-ray from 60Co source, a new ESR spectrum appeared, the color of which was at a certain time deepened.
At the results of these studies, it will partially be explained that the built-in color of anodized alumina films would be caused by the fact that electrons are trapped by the crystalline defects or other places corresponding to vacancies of glassy alumina.
