Spectroscopic properties of cerium in sol-gel glasses

Glasses containing Ce were prepared by the sol-gel method at elevated temperatures. Two parallel series, one in air and one in nitrogen atmosphere, were obtained. The main constituent of the glasses was silica SiO₂ obtained by hydrolysis of ethoxysilane (TEOS). Spectroscopic properties of the glasses were studied by time-resolved and steady-state luminescence spectroscopy. In the present paper we made an effort to distinguish between the blue luminescence arising from Ce(III) and that obtained from the silica host which is connected with defects in the matrix. While the spectra of both pure silica and Ce activated silica excited at 337 nm or longer wavelength have the similar emission peaking between 400 and 450 nm, the emission of silica is broader and its decay time shorter than that of Ce(III). It seems that Ce quenches the luminescence of the silica centers. When excited at 308 nm by an excimer laser we detect short-lived emission of Ce(III) peaking between 350-380 nm which may be due to excitation to the conductivity band and subsequent recombination of the excited electrons with a hole.