Viscosity and Structure of Lithium Sodium Borosilicate Glasses

Viscosity and structure of sodium borosilicate glass doped with Li2O were investigated by the rotating crucible viscometer and Fourier infrared spectrum. The melting temperature and activation energy for viscous flow of the studied melt were derived on the basis of Arrhenius equation, in order to reveal the effects of Li2O substitution on the behavior of sodium borosilicate glass. As expected, introduction of Li2O decreases the viscosity of elevated temperature melt, however, the results develop in the opposite direction when the concentration of Li2O is over 1.00 mol. This abnormal phenomenon can be explained in terms of the high ionic field of Li2O and the proportions of [BO3] and [BO4]. As the increase of Li2O, the boosting of the peak which is located about 1400 cm-1 due to the asymmetric stretching relaxation of B-O bond of [BO3] proves the decrease of free oxygen.