Thermal expansion and characteristic points of –Na2O–SiO2 glass with added oxides

A differential method with an optical lever system was used to determine the thermal expansion of the glasses based on Na2O–SiO2 and containing the following oxides: Al2O3, CaO, TiO2, ZnO, Al2O3–TiO2, CaO–TiO2, or ZnO–TiO2. The determination was carried out on both as-drawn and annealed rods. The influence of the thermal history as well as of the added oxide(s) on the thermal expansion of glasses is dealt with in this paper. The experimental results for the thermal expansion of annealed rods show that the addition of CaO–TiO2 in the glass has the lowest value while the addition of CaO in the glass has the highest value for the coefficient of linear expansion. At the same time, the characteristic points of the annealed glasses, determined from the expansion-temperature curves, show that the addition of ZnO in the glass has the lowest values while the addition of TiO2 in the glass has the highest values.