Characterization of the transition xerogel-glass of materials prepared with modified teos: The case of Cu2+

Abstract The Xerogel-glass transition was studied using the following techniques: UV-VIS, RPE, High Resolution Electron Microscopy, Transmission Electron Microscopy and X-ray analysis. The electron spectroscopy and paramagnetic resonance results demonstrate that the CU 2+ ions are at two different sites in the SiO 2 lattice—one superficial and the other inside the bulk. The electron microscopy results showed crystalline areas observed by selected area diffraction, and we obtained lattice resolution of these areas using high resolution electron microscopy. The crystalline aggregates are due to the metallic ions which were added as nitrates or acetates; some of these aggregates were localized in the external edges of the SiO 2 grains and others on the surface of the same SiO 2 . X-ray analysis showed an amorphous material. No characteristic peak of any crystalline substance was found.