中文摘要：

以MgO-Al2O3-CeO2复合体系为烧结助剂,采用放电等离子烧结工艺制备氮化硅陶瓷.研究了MgO-Al2O3-CeO2含量、烧结温度对氮化硅陶瓷显微结构及力学性能的影响;探讨了复合烧结助剂作用下氮化硅陶瓷的烧结机理.结果表明：当混合粉体中Si3N4、MgO、Al2O3和CeO2的质量比为91∶3∶3∶3、烧结温度为1 600℃时,氮化硅烧结体相对密度（99.70％）、硬度（18.84 GPa）和断裂韧性（8.82 MP·m^1/2）达最大值,晶粒以长柱状的β相为主,a-Si3N4→β-Si3N4相转变率达93％;当混合粉体中Si3N4、MgO、Al2O3和CeO2的质量比为88∶4∶4∶4、烧结温度为1 600℃时,烧结体抗弯强度（1 086 MPa）达到最大值.

英文摘要：

The Si3N4 ceramic were prepared by spark plasma sintering using multiply MgO–Al2O3–CeO2 system as the sinteringadditives. Effects of sintering additive and sintering temperature on the microstructure and mechanical properties of silicon nitrideceramic were investigated. The sintering mechanism of silicon nitride in the presence of the sintering additive was discussed. Theexperimental results show that the silicon nitride ceramic sintered with a mixed powder of Si3N4：MgO：Al2O3：CeO2 of 91：3：3：3 （inmass ratio） at 1 600 ℃ has the maximum relative density of 99.7%, the hardness of 18.84 GPa and the fracture toughness of 8.82MPa·m^1/2. The β-Si3N4 grains have an elongated shape, and the transition rate of α-Si3N4→β-Si3N4 reaches 93%. The silicon nitridesintered with a mixed powder of Si3N4： MgO： Al2O3： CeO2 of 88：4：4：4 （in mass ratio） at 1 600 ℃ has the optimum bending strengthof 1 086 MPa.