Sintering and Microstructure of Silicon Nitride with Magnesia and Cerium Additives

Abstract This paper deals with the pressureless sintering and microstructure of Si 3 N 4 –MgO–CeO 2 ceramics. The sintered Si 3 N 4 –MgO–CeO 2 ceramics achieved a relative density of 98.5% and a bending strength of 950 MPa. XRD, TEM and EDAX analysis indicated that the main composition of the glassy phase in the sintered Si 3 N 4 –MgO–CeO 2 ceramics was cerium silicate and that it hardly contained any MgO: during sintering, MgO would crystallize. Abnormal grain growth occurred at 1850°C, which led to microcracks and dislocation. Some silicon whiskers were growing in fractal patterns during TEM observation, which provided a good experimental example for further study of fractal growth.