The SiO2–P2O5 binary system: New data concerning the temperature of liquidus and the volatilization of phosphorus

The SiO2–P2O5 binary system is not well known. The aim of this work is to enhance the description of this quasibinary system. Volatilization of phosphorus, liquidus temperatures and phases crystallization were studied by TGA, X-ray diffraction, NMR and SEM after quenching systems of two compositions (50 wt% SiO2–50 wt% P2O5 and 75 wt% SiO2–25 wt% P2O5). At high temperature (>950 °C), volatilization of phosphorus in the SiO2–P2O5 binary system occurs. The liquidus temperatures are close to the ones proposed in the literature. The experimental results show the crystallization of SiP2O7 in four different polymorphs and the formation of the Si5O(PO4)6 oxide phase.