Preparation and Mechanical Property of Si_3N_4-MgO-Al_2O_3 by Spark Plasma Sintering Technique

In the present study, α-Si_3N_4 was prepared by using spark plasma sintering (SPS) technique with MgO and Al_2O_3 as the sintering additives. The SPS sintering behavior and mechanism were discussed. The relationship between the content of sintering additives, sintering temperature and relative densities of the samples was analyzed. The phase composition was analyzed by XRD, the microstructure of the fracture surface was observed by SEM and the bending strength was tested by three-point method. The results show that when the sintering temperature is 1300~1500℃ and the content of sintering additives is 6%~10%, the relative density of sintered samples is between 64% and 96%; when the sintering temperature reaches 1400℃ and the content of sintering additives is 10%, the samples could be fully dense sintered with the relative density up to 95%. The sintering mechanism is found to be liquid phase sintering. The bending strength of the sintered samples is 50~403MPa and had close relation with the relative density.