Texture and Microstructure in Hot-Pressed Si3N4

The texture formation in hot-pressed Si3N4-ceramics was investigated by means of X-ray diffraction. A ring-fibre texture is observed with the basal plane (002) perpendicular to the hot-pressing axis. The texture index of hot-pressed Si3N4 depends on the starting powder mixture and process parameters. The α→β phase transfomation and the growth of β-Si3N4 needlelike grains are correlated with the texture. Measurements of fracture toughness and aspect ratio confirm the correlation with microstructure. The structure is the result of crystal growth and flow process during hot-pressing.