Optical Behavior of ZnS:Cu Microcrystals Embedded in Porous Silica Gels
Emission and excitation spectra of ZnS:Cu microcrystals trapped in porous silica xerogels are presented. This system is characterized by intense, long-lived green emission at room temperature. It was observed that this emission was greatly reduced after compressing the xerogel samples.
Optical centers of cerium in silica glasses obtained by the sol-gel process
Abstract A spectral-luminescent study of Ce-containing silica gel-glasses doped at the sol stage and by impregnating porous xerogels with activator chloride salt solutions has been performed. The influence of the degree of doping and redox conditions of vitrification on the activator charge state and the content of hydroxyl ions and chlorine in the glass is considered. The preservation of the glass phase composition and the non-linear increase in the visible absorption intensity with increasing activator concentration from 5 × 1017 to 3.0 × 1020 ions/cm3 are noted. It is concluded that there are two main types of optical centre. It is assumed that they represent Ce(III) oxygen complexes whose nearest surrounding includes quadruply charged (the first type) and triply charged (the second type) ions of cerium. Evidence has been obtained in favor of the superexchange excitation transfer to the central ion of Ce(III) oxygen complexes from photoreduced to the triply charged state of the same ion name of Ce(IV) oxygen complexes.
Infrared Spectra of a Water‐Containing Glass
Infrared absorption was measured on an NajO-K2O-ZnO-Al2O3-SiO2 glass with up to ∼11 wt% water. Fundamental and overtone-combination bands were observed at 1.41, 1.91, 2.22, 2.87, and 6.1 μm. Molar absorptivities were determined for the hydrated glass for H2O and OH levels using the molar absorptivity calculated for the 2.22-μm band in the as-melted glass. By this procedure the concentration of molecular water and OH groups could be determined separately. These results show that the OH content of the hydrated glass, as determined from the 2.22-μm band, is constant at >7 wt% H2O; additional H2O is attributed to molecular water only. Good agreement was found between these data and H2O/OH molecular ratios obtained from NMR.