中文摘要：

以冲击波合成的立方氮化硅（γ-Si3N4）粉体为原料,添加Y2O3-Al2O3-La2O3系烧结助剂,进行了超高压烧结,研究了在不同烧结温度与压力下,烧结样品的相对密度、力学性能、物相变化及显微结构。经5.4～5.7 GPa和1670～1770K,保温保压15 min超高压烧结后,烧结制备的氮化硅陶瓷主要由长柱状晶粒组成,显微结构均匀,γ-Si3N4已完全转化为β-Si3N4。烧结样品的最高相对密度与Vickers硬度分别为99.16%,23.42GPa。

英文摘要：

Silicon nitride ceramics were prepared by super-high pressure sintering using cubic silicon nitride powders synthesized by the shock-compression technique as raw materials and with Y2O3-Al2O3-La2O3 mixtures as additives.The relative density,mechanical properties,phase transition and microstructure of sintered compacts under different pressures and temperatures were investigated. Silicon nitride ceramics obtained at pressures of 5.4-5.7 GPa and temperatures of 1 670-1 770 K for 15 min were mainly composed of elongatedβ-Si3N4 rod crystals with disordered orientation and uniform microstructures,and the cubic Si3N4 in raw powder was com- pletely transformed intoβ-Si3N4.The highest relative density and Vickers hardness in the as-sintered samples were 99.16% and 23.42 GPa respectively.