'Low-Frequency Dynamics in Silica Xerogels'

Brillouin and Raman experiments have been performed in hydrogenated silica sol-gel and vitreous silica samples made by sol-gel processes (xerogels) and by the melting powder method. The aim of this work has been the study of the low-frequency dynamics of sol-gel systems in comparison with that of amorphous silica. By thermal treatment of the gel a progressive densification of the system was obtained: at 500°C we obtained densification (temperature well below the usual temperatures); at higher temperature (≈700-800°C) the pores were eliminated and the dynamics (Brillouin shifts, quasielastic scattering, and Boson peaks) became equivalent to that of fused silica.