Effect of seed crystal properties on the microstructure of Si3N4 ceramics

The effect of seed crystal properties on the microstructure of Si3N4 ceramics was investigated. Three beta-Si3N4 powders with average grain size of 0.74, 5.84 and 21.66 mu m and beta-Si2N4 whiskers were used as seeds. Seeds (2 mass%) were added to the mixture of alpha-Si3N4 and sintering aids, and the mixture was hot-pressed at 1850 degrees C for 8h. Growth of large rodlike-grains was enhanced by the micron-sized single-crystalline beta-Si3N4 particle. Crushed beta-Si3N4 whiskers were similarly effective in growing rodlike-grains. On the contrary, polycrystalline beta-Si3N4 particles and submicron-sized beta-Si3N4 particls did not affect greatly the final microstructure.