Effect of Replacement of SiO2 ↔ (Al2O3 + BaO) on the Structure and Properties of Alkali-Free Silicate Glasses

Abstract

The effect of replacing silicon dioxide with a combination of aluminum and barium oxides in alkali-free silicate glasses is studied. The concentration of silicon dioxide in the series of glasses studied decreases from 49 to 34 mol %, while that of aluminum oxide and barium oxide increases from 4 to 9 and from 15 to 24 mol %, respectively. The content of the remaining oxides remains constant. The elemental and phase composition of the glasses is determined using inductively coupled plasma spectroscopy, energy-dispersive spectroscopy, X-ray diffraction, and scanning electron microscopy; the thermal properties are determined using differential scanning calorimetry and dilatometry; and the structure of the glasses is determined using Raman spectroscopy and infrared spectroscopy. It is shown that replacing silicon dioxide with a mixture of aluminum and barium oxides does not lead to a noticeable change in the structure of the glass or its structure-sensitive properties, such as the coefficient of linear thermal expansion (CLTE) and glass transition temperature T_g, as well as the transition to a fluid state temperature T_f. During heat treatment of glass, crystals precipitate depending on the composition and temperature: coesite, celsian, or double barium–calcium silicate.