Abstract
Viscosity measurements made between 10 2 and 10 12 dPa s are reported for six (25 − x)Na 2O · xTiO 2 · 75SiO 2 glasses ( x = 0, 1, 2.5, 5, 7.5 and 10). The methods of falling ball, rotational viscosimetry and dilatometric axial deformation rate measurement were used to cover the studied viscosity range. The values of dilatometric glass transition temperature are also reported. Obtained temperature and compositional dependencies of viscosity confirmed the validity of the Adam-Gibbs viscosity equation. The individual molar free hindrance energies B e and the configurational entropies S conf( T g) resulted from the least-squares regression treatment for each glass composition. Both the molar free hindrance energies and the configurational entropies depend on the TiO 2 content in a similar fashion, indicating the changes in the titanium structural role in the compositional range studied. These results are in qualitative agreement with the analogous dependence of glass transition temperature.
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