Effects of SnO2-SiO2-MgO-Bi2O3-Y2O3 Additions on Liquid Phase Sintering Silicon Nitride

Abstract

Si3N4 ceramics were sintered at relatively low temperature of 1400-1650 °C with additives from the SnO2-SiO2-MgO-Bi2O3-Y2O3 system. The degree of densification, α-β transformation, mass loss and microstructure were measured as a function of additives composition, sintering temperature, and nitrogen gas pressure. Specimen prepared from 3 mass% SnO2, 3 mass% SiO2, 3 mass% MgO, 6 mass% Bi2O3, and 5 mass% Y2O3 as the sintering additive could be sintered to almost full density at relatively low temperature as 1550 °C for 2 h under ambient pressure of nitrogen atmosphere. The α-β transformation was not completed at this condition. The mass loss was relatively high due to the evaporation of SiO2, MgO and Bi2O3. However, the resulted dense materials have high bending strength.