The anodic oxidation of neodymium

The anodic oxidation of neodymium was investigated by the galvanostatic technique in Na2HPO4-ethylene glycol solution. From the combination of measurements of ac capacity and of specular reflectivity, a refractive index was obtained for the oxide films as a function of wavelength and the value of apparent dielectric constant of the films for which sesquioxide Nd2O3 was assumed to have been produced. It was found that the film thickness could be determined from the wavelength of both maximum and minimum specular reflectivities due to interference, and that a linear relationship existed between the film thickness and the formation voltage. The slope of this linear line was 10.0 A V-1 or a mean field of 1.00 x 107 V cm-1 at 1 mA cm-2. The apparent current efficiency estimated from the thickness of the film vs passed charge plots scarcely depended on the latter and its value was about 0.52, assuming that the film composition was Nd2O3. (author)