Liquidus Temperature of SrO-Al_2O_3-SiO_2 Glass-Forming Compositions

摘要

Despite the important role of strontium aluminosilicate glasses in various technologies, there is no available phase diagram for this ternary system in the ACerS-NIST Phase Equilibria Diagrams Database. Establishing the liquidus surface (liquidus temperature T_(liq) and primary devitrification phase) is crucial for glass composition design, because the liquidus temperature is intimately connected with the glass-forming ability of the melt. In this work, we have determined the liquidus surface by X-ray diffraction phase analyses of isothermally reacted samples from powder mixtures of 24 compositions. In the composition range of interest for industrial glasses, T_(liq) tends to decrease with increasing strontium-to-alumina ratio. We find that cristobalite, mullite, and slawsonite are the dominant devitrification phases for the compositions with high SiO_2, SiO_2+Al_2O_3, and SrO contents, respectively. By comparison with the phase diagrams for CaO-Al_2O_3-SiO_2 and MgO-Al_2O_3-SiO_2 systems, we have found that for the highest [RO]/[Al_2O_3] ratios, T_(liq) exhibits a minimum value for R = Ca. Based on the phase diagram established here, the composition of glass materials, for example, for liquid crystal display substrates, belonging to the SrO-Al_2O_3-SiO_2 family may be designed with a more exact control of the glass-forming ability by avoiding the regions of high liquidus temperature.