Physicochemical Properties of Glasses of the Na2O–B2O3–SiO2–Fe2O3 System in the 6Na2O/70SiO2 Section

Resumo

Glasses of the 6Na₂O–(24–х)B₂O₃–70SiO₂–хFe₂O₃ system with x ranging from 2 to 10 mol % are studied by dilatometry and X-ray powder diffractometry. The density of the glass is measured and the molar volume is calculated. The heat treatment of the glass is carried out at 550 and 700°C for 96 and 2 h, respectively. Magnetite is formed in the heat-treated glasses and its content increases with the growth of the Fe₂O₃ concentration. In the glasses containing from 4 to 8 mol. % of Fe₂O₃, cristobalite is formed after treatment at 700°C for 2 h. An increase in the density and the glass transition temperature and a decrease in the molar volume is observed with the growth of the iron oxide content.