Synthesis of porous silicon nitride by using seed crystals

Synthesis of porous silicon nitride (Si3N4) by using seed crystals was stud ied. Seed crystals were prepared by heating a powder mixture of alpha -Si3N 4 and sintering aids. Y2O3 was the most effective additive for obtaining se ed crystals of high aspect ratio. By adding rod-like seed crystals to alpha -Si3N4 starting powder, porous Si3N4 with relatively high porosity could b e fabricated. In the case of adding 50 vol% seed crystal, rod-like grains w ere well combined, forming a framework. The effect of sintering additives o n porosity of the porous body was also studied. By adding 5 mass% Y2O3 and 2 mass% Al2O3 as sintering additives, the porosity of sintered body was red uced.