The influence of water on the structure and glass transition of sodium borate supercooled liquids from the small-angle X-ray scattering data

Sodium borate glasses containing 5.5, 15, and 25 mol % Na₂O are synthesized under different conditions (different temperatures and times of heat treatment, treatment under vacuum) and studied by the small-angle X-ray scattering (SAXS) technique. The temperatures of the glass transition and the transition from the supercooled liquid state to the noncrystalline solid state are determined from the temperature dependences of the SAXS intensity. It is revealed that a decrease in the water content leads to an increase in the glass transition temperatures and to an increase in the SAXS intensity in the case of glasses containing 15 and 25 mol %. It is assumed that this behavior can be associated with the increase in the isothermal compressibility.