SiO2 xerogel and aerogel treated up to 900oC exhibit amorphous behavior. A narrowing of
the XRD peak accompanied by an increase in its intensity with increasing in the temperature
of the preparation indicate an increase in the structural organization of the samples (Figure
3a and 3b). Characteristic reflections of crystobalite and tridimite appear at 1100oC for both
the samples. The intensity of the xerogel peaks are larger than the aerogel ones.