DENSIFICATION AND SINTERING KINETICS IN SINTERED SILICON-NITRIDE

The sintering sequence of Y2O3-Al2O3-doped Si3N4 was investigated with respect to the relationship between densification, alpha --> beta-transformation, and microstructural development. Quenching studies were performed to reveal these interactions during a complete sintering cycle. Isothermal studies were conducted to examine the sintering kinetics and compared to Kingery's liquid-phase sintering model. The bulk density increased to > 90% of theoretical density with only minor transformation taking place. Major transformation occurred in a late sintering stage and was accompanied by the development of elongated grains. The kinetic order of the densification process, taking into account an appropriate correction, was larger than any of the rate exponents predicted by the Kingery model, indicating that other single or mixed mechanisms were active.