Abstract
The EPR spectroscopy of Mn2+ spin label was used to investigate the structural evolution of SiO2 xerogel. Analysis of the EPR spectra shows a decrease of the half width of spectral lines of the Mn2+ hyperfine structure. This fact is caused by retardation of the spin label mobility as a consequence of densification and strengthening of the xerogel structure with the treatment temperature. The same features were observed in the measured spectra of the heat treated xerogel during its ageing. A model considering a similar mechanism of structural relaxation during thermal evolution and ageing of xerogel at laboratory temperature was proposed and statistical analysis was used to verify its reliability.