Structural Interpretation of Immiscibility in Oxide Systems: I, Analysis and Calculation of Immiscibility

Abstract

Crystal chemistry principles are applied to the quantitative interpretation of immiscibility in nineteen binary and eight ternary glass systems. Using ionic radii and one of two coordination types, two methods are given for the calculation of immiscibility in binary systems. The additive density method gives agreement with experimental results in both the borate and silicate systems to within about 5 mole %. The oxygen‐volume method agrees, in general, to within 2 mole %. The maximum extent of immiscibility in ternary borosilicate systems can also be calculated. The importance of the electrostatic bond strength, defined as the valence divided by the coordination number, is discussed in relation to shape of liquidus curve, cation coordination type, and charge distribution on the network‐former tetrahedra. Implications of the analysis to the structure of glass are presented.