Application of spark plasma sintering for consolidation study of β-sialon ceramics

Investigated were the spark plasma sintering (SPS) of β-sialon ceramics according two different schemes: the simple sintering of pure β-Si5AlON7 powder and the reactive sintering of mixture of α-Si3N4 and β-Si2Al4O4N4 powders. The high-density homogenous structure of simple sintered β-Si5AlON7 ceramics was achieved at maximum temperature of isothermal holding Tmax = 1550 °C by using submicron raw powder. While ceramics from coarse raw powder had porous structure and was subjected to thermal decomposition at Tmax ≥ 1750 °C. Three specific temperature intervals were revealed for the reactive sintering. At Tmax ≤ 1650 °C, the shrinkage rate attained the values sufficient for densification near to a theoretical density, without any changes in the size/morphology of starting particles and without transformation of starting α-Si3N4 into β-sialon. At Tmax = 1700–1750 °C, starting α-Si3N4 was found to undergo transformation into β-sialon but without marked changes in the size/morphology of starting particles. At Tmax ≥ 1750 °C, the sintered ceramics exhibited a marked growth in the size and change in the shape of sintered particles.