Specific features of the kinetics of structural relaxation in microinhomogeneous glasses

Abstract

The kinetics of structural relaxation in vitreous boron oxide and sodium borate glass containing 5.5 mol % Na2O during isothermal treatment at a number of temperatures after cooling from high temperatures and a sharp increase in the temperature of samples stabilized at T < Tg for different times is studied by the small-angle X-ray scattering (SAXS) technique. It is shown that, as the fictive temperature of samples approaches the temperature at which the supercooled liquid transforms into a noncrystalline solid state, the times of development of a structural inhomogeneity that arises in the samples after a drastic increase in the temperature increase considerably in a narrow temperature range (1–2 K). The intensity of small-angle X-ray scattering by a micro-inhomogeneous structure formed in the course of relaxation processes in chemically inhomogeneous glasses substantially exceeds the SAXS intensity observed during structural relaxation of vitreous boron oxide. This is associated with the increase in the sizes of structural inhomogeneity regions in the matrix in heterogeneous samples as compared to the sizes of similar regions in homogeneous glasses. Stresses arising in heterogeneous samples during structural relaxation are responsible for the interference effects that substantially affect both the SAXS intensity at angles close to zero and, correspondingly, the light scattering intensity.