Abstract
The effects of substituting Na+ and Ca2+ ions by Mn2+ ions in the glass composition Na2O 16, CaO 10 and SiO2 74 and partial replacement of this composition by MnO and/or Fe2O3 on high temperature viscosity, thermal expansion and chemical durability were studied. On replacing Na+ ion by Mn2+ ion the high temperature viscosity and coefficient of thermal expansion decreased and the chemical durability increased. Substitution of Ca2+ ion by Mn2+ ion had similar effect but to lesser extent. On partial replacement of the glass composition by MnO and/or Fe2O3, the high temperature viscosity decreased and chemical durability increased.