Phase relationships in the system Si3N4–SiO2–Yb2O3

Abstract

Phase relationships in the system Si3N4−SiO2−Yb2O3 have been investigated at 1750 °C and compared with those in the system Si3N4−SiO2−Y2O3. Two types of ytterbium silicon oxynitride, Yb2Si3O3N4 (tetragonal) and Yb4Si2O7N2 (monoclinic), were confirmed to exist. The x-ray powder diffraction data of two compounds were indexed based on the space group and unit cells. Melting temperature of Yb4Si2O7N2 was determined as 1870 °C. Yb4Si2O7N2 is a better intergranular phase of silicon nitride ceramics for its high melting temperature.