Brillouin Scattering Study of Liquid Glass Transition in Lithium Borate Glass

概要

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Elastic properties of different compositions of lithium borate glasses $x$Li2O$\cdot$$(1-x)$B2O3 ($x=0.06--0.28$) were investigated in the temperature range from 25 to 600 °C by Brillouin scattering spectroscopy. The composition dependence of the lithium borate glass system shows a stiffening tendency and a higher onset temperature of softening with increasing mole fraction of Li2O. We successfully observed the change in longitudinal elastic modulus in the vicinity of the glass transition temperature ($T_{\text{g}}$). The elastic moduli show a marked temperature dependence above the glass transition temperature $T_{\text{g}}$, while they show little change below $T_{\text{g}}$. These results strongly relate to the structural conversion of cross-linking borate units from triangular BO3 to tetrahedral BO4 units by the addition of Li2O. The increase in lithium oxide enhances the glass network integrity in the composition range of this study. A significant decrease in the elastic modulus above $T_{\text{g}}$ can be attributed to the association of boroxol ring deformation and a change in the coordination number of boron atoms. These elastic properties were discussed in comparison with lithium silicate glass.
2006-05-30