Sintering and microstructure of silicon nitride with magnesia and cerium additives

This paper deals with the pressureless sintering and microstructure of Si3N4–MgO–CeO2 ceramics. The sintered Si3N4–MgO–CeO2 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 Si3N4–MgO–CeO2 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.