Résumé
Low-OH-content silica samples having fictive temperatures in the interval 1000–1500°C, have been studied by small-angle X-ray scattering using synchrotron radiations both at room temperature and from 20 to 1500deg;C. 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 Tg.