SINTERING PROCESS OF Y2O3-ADDED SI3N4

The sintering process of Y2O3-added Si3N4 has been investigated by dilatometry and microstructural observations. Densification was promoted above 1440 ° C by the formation of eutectic melts in the Y2O3-SiO2-Si3N4 triangle. However, the dilatometric curves indicated no shrinkage corresponding to the rearrangement process, despite liquid-phase sintering. The kinetic order for The Initial-stage sintering was 0.47 to 0.49. These values indicated that the phase-boundary reaction was rate controlling. The apparent activation energy (323 kJ mol-1) was smaller than the dissociation energy for the Si-N bond (435 kJ mol-1). ESR data and lattice strain indicated that the disordered crystalline structure of the Si3N4 starting powder promoted the reaction of Si3N4 with eutectic melts. After a period of initial-stage sintering, the formation of fibrous β-Si3N4 grains resulted in interlocked structures to interrupt the densification. © 1990 Chapman and Hall Ltd.