The enthalpic relaxation of the title glasses, studied by differential scanning calorimetry, is well described by a mathematical
model based on the stretched exponential relaxation function with the relaxation time proportional to the actual viscosity.
The dependence of viscosity on temperature and the fictive temperature was expressed by Mazurin's approximation. The relaxation
parameters obtained correlated significantly with the glass composition, indicating the changes in the structural of the TiO2 role near a TiO2 content of 3–4 mol%.