Abstract
Density and concentration fluctuations have been investigated in a 3 mol % GeO2 doped silica glass as a function of the fictive temperature (the temperature at which the structure of the supercooled liquid has been frozen-in to form the glass) by small angle x-ray scattering measurements. The fluctuations increase in a way is quite similar to that observed for pure silica glass as a result of density fluctuation fictive temperature dependence. Fluctuations have also been studied in glasses containing different amounts of GeO2 up to 21 mol % GeO2. The fluctuations are shown to increase very strongly with germanium amount as a result of strong concentration fluctuation increase. This observation is in agreement with already observed excess losses in light scattering measurements.