Abstract: Densification, phase transformation and fracture toughness were studied in hot-pressed Si3N4 seeded by in-house produced large, elongated β- Si3N4 seeds. A mixture of Y2O3-Al2O3 was used as the sintering aid. Concentration of seeds were varied from 0 to 6 wt pct and the sintering time at 1700℃ was varied from 1 to 4 h. Maximum fracture toughness of 9.0 MPam1/2 was measured in samples containing 5 wt pct seeds, hot pressed at 1700℃ for 4h.

Key words: In-situ composites, Seeds, Hot-pressing, Silicon nitride