Temperature dependence of the density fluctuations of silica by small-angle X-ray scattering

Low-OH-content silica samples having fictive temperatures in the interval 1000-1500degreesC, have been studied by small-angle X-ray scattering using synchrotron radiations both at room temperature and from 20 to 1500degreesC. The limit for zero-angle X-ray scattering intensity is analysed in term of density fluctuations. We demonstrate that density fluctuations are strongly related to structural relaxation, both depend on thermal history (i.e. the fictive temperature) of the sample, in the temperature range below T-g.