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

Abstract The SiO 2 –P 2 O 5 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% SiO 2 –50 wt% P 2 O 5 and 75 wt% SiO 2 –25 wt% P 2 O 5 ). At high temperature (>950 °C), volatilization of phosphorus in the SiO 2 –P 2 O 5 binary system occurs. The liquidus temperatures are close to the ones proposed in the literature. The experimental results show the crystallization of SiP 2 O 7 in four different polymorphs and the formation of the Si 5 O(PO 4 ) 6 oxide phase.