Studies in sol-gel glasses with incorporation of Cu and Fe, using PAS, X-ray diffraction and EPR

SiO2 Glasses with incorporation of either Cu or Fe were prepared by the sol-gel process and annealed in air at temperatures within the range of 100 to 500 degreesC. The samples were characterized using Visible Photoacoustic Absorption Spectroscopy (PAS), X-ray powder diffraction and Electron Paramagnetic Resonance (EPR). Under the annealing both systems show significant changes in composition, producing an evolution in the optical absorption spectra. In both systems, the formation of the metal oxide particles is observed after annealing at or above 300 degreesC. The optical and EPR spectra are interpreted in terms of the coordination of the metal ions using the ligand field theory. It is observed that the color of the samples has strong change with both the type of metal incorporated and with the annealing temperature.18320721