Specific absorption spectra of cerium in multicomponent silicate glasses

Abstract

Photoionization of glass requires photon energies larger than the bandgap of the glass matrix. To shift the photosensitivity of a glass to longer wavelengths, it is common to add a sensitizer, e.g. cerium. Cerium has two valence states but only the Ce 3+ is UV-photoactive. Hence, we present a spectral method that allows determining specific absorption spectra of both valent states of cerium in two different silicate glasses. Two overlapped absorption spectra, one for Ce 3+ and one for Ce 4+, were observed in soda lime silicate glass. It was found that both spectra consist from two Gaussian bands. Specific absorption of each ion was calculated on the basis of balance equations written for glasses melted under different redox conditions and used to estimate the absolute concentration of each ion. An identical analysis was performed on a photosensitive multicomponent silicate glass (photo-thermo-refractive (PTR) glass). It was found that absorption band of Ce 3+ in PTR glass is shifted to short wavelength region due to the presence of fluorine while absorption spectra of Ce 4+ are identical. The effect of UV-exposure on absorption spectra of cerium was studied. An absorption spectrum of photo-ionized Ce 3+ is not identical to that of Ce 4+: UV-exposure induces a new band resulting from Ce 3++ and electron color centers.