Properties and structure of germanium-containing lithium aluminoborate glasses

Abstract

Glasses of the system Li2O–Al2O3–GeO2–B2O3 have been investigated. The effect of replacement of the B2O3 by GeO2 on the physicochemical properties of the glasses has been studied. The density and the refractive index were found to increase as the GeO2:B2O3 ratio (r) increases. In contrast, the molar volume was found to decrease as r increases. Dilatometric measurements showed that the thermal expansion coefficient (α) increases with the increase of r whereas both of the glass transition temperature (Tg) and the softening point (Ts) decreases with increasing r. Fourier transform infrared (FTIR) spectroscopy revealed that BO3 structural units increase at the expense of BO4 units as r increases. It is indicated also that GeO6 units are the preferred germanium structural units that participate into the glass network. The electrical conductivity was found to decrease with increasing r. This was attributed to the large difference between the two atoms (Ge and B), which increases the stability and therefore decreases the conductivity of the investigated glasses. The conductivity results were correlated with those from the FTIR study.