Influence of annealing on optical properties of cerium doped soda-lime-silicate glasses

Effects of annealing on optical absorption (OA) and photoluminescence (PL), emission and excitation spectra from a cerium doped soda-lime-silicate glass ion-exchanged with silver were investigated. Annealing experiments were performed at temperatures of 350 and 400 degreesC, far below the 569 degreesC transition temperature measured for the doped glass. Evidence of surface-plasmon resonance of metallic silver nanoparticles and its subsequent disappearance in the OA spectra by annealing effects are reported. In this case, the reduction of Ag- to elemental silver and further reoxidation are governed in part by the reaction Ce3+ +Ag+ <----> Ce4+ +Ag-0. Results are in agreement with a preferential formation of silver nanoparticles at the surface, where the strain energy is more easily relaxed. On the other hand. PL spectra are also affected by the annealing, principally excitation spectra. Analyses of these spectra by de-convolution into three Gaussian shapes were carried out. The influence of annealing has a special significance for the excitation component centered between 3.94 and 3.84 eV (similar to 315 and 323 nm), related to Ce3+ centers. Superficial increase in the number of Ce4+ partially prevents excitation of remaining Ce3+ ions and, therefore, enhances self-absorption in the glass. The main changes in the OA and PL spectral features are discussed in terms of the reducing role of Ce3+ ions and on the basis of thermal relaxation of the surface tensile stress caused by differences in size between Ag+ and Na+ ions. (C) 2001 Elsevier Science B.V. All rights reserved.