Photoelectrochemical studies were performed using passivated titanium electrodes. The passive films were formed by anodization of Ti in 0.5M H2SO4 galvanostatically with current densities between 2 and 100 mA/cm 2, with a constant passed charge of 4 A 9 s/cm 2. Photecurrent spectra in 1M NaOH, short-circuit photocorrosion in 0.5M H2SO4 and changes of refractive index suggest the dependence of oxide properties on the anodization rate. With increasing current density j of anodization, the bandgap for indirect transitions becomes smaller, the refractive index increases, and the photocorrosion increases at j = 100 mA/cm 2. The time dependence of photocorrosion indicates that the quality of the oxide is not the same along the cross section. X-ray diffraction confirms that the film is composed of anatase and ruffle phases of polycrystalline TiQ with very fine grains. The fraction of futile increases at large current densities and the layer is more porous, especially after the anodization breakdown had occurred.
5 M H2SO4 depend on the anodization rate represented by the current density j. The bandgap energies of both direct and indirect transitions decrease with increasing current density. Refractive index and photocorrosion increase at j = 100 mA/cm2. As revealed from XRD, the film is composed of anatase and rutile phases of polycrystalline TiO2. The rutile fraction increases at high current densities and the film is more porous. The quality of the oxide is not the same along the cross section as indicated from the time dependence of the photocorrosion. -(MIKULA, M.; BLECHA, J.; CEPPAN, M.; J.
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