Abstract
The densification behavior and strength of sintered reaction bonded silicon nitrides (SRBSN) that contain Lu2O3-SiO2 additives
were improved by the addition of fine Si powder. Dense specimens (relative density: 99.5%) were obtained by gas-pressure sintering
(GPS) at 1850oC through the addition of fine Si. In contrast, the densification of conventional specimens did not complete at
1950oC. The fine Si decreased the onset temperature of shrinkage and increased the shrinkage rate because the additive helped
the compaction of green bodies and induced the formation of fine Si3N4 particles after nitridation and sintering at and above 1600oC.
The amount of residual SiO2 within the specimens was not strongly affected by adding fine Si powder because most of the SiO2
layer that had formed on the fine Si particles decomposed during nitridation. The maximum strength and fracture toughness of
the specimens were 991 MPa and 8.0 MPa·m1/2, respectively.