The role of MgSiN2 during the sintering process of silicon nitride ceramic

Abstract The reaction process between MgSiN 2 SiO 2 and Si 3 N 4 was investigated by analyzing the composition change of the powder mixture of 61 wt% MgSiN 2 , 34 wt% SiO 2 and 5 wt% α-Si 3 N 4 after heat treatment at different temperatures. The phase and chemical compositions of the grain boundary phase in the silicon nitride ceramic was analyzed by x-ray diffraction, transmission electron microscope, and energy-dispersive x-ray spectroscopy. The results demonstrated that MgSiN 2 reacted with the surface silica and Si 3 N 4 to form Mg–Si–O–N liquid phase, which promoted the consolidation densification of silicon nitride powders through liquid-phase sintering mechanism. The amount of Mg–Si–O–N glass boundary phase using MgSiN 2 as additives is much less than that using the same amount of MgO additive, owing to the lower oxygen concentration and higher nitrogen content.