Fabrication of dense β-SiAlON by a combination of combustion synthesis (CS) and spark plasma sintering (SPS)

First, β-Si6−zAlzOzN8−z (z = 1-4) powders were combustion-synthesized from well-mixed powders of Si, Al, and SiO2 under a low nitrogen pressure of 1 MPa using β-SiAlON (calculated z = 1.14) as the diluent. Then, the synthesized powders were subjected to spark-plasma-sintering (SPS) in vacuum for 12 min under a stress of 50 MPa and a temperature of 1600 °C, without any sintering additives. X-ray diffraction (XRD) analysis revealed that a small amount of unreacted phase was found in the combustion-synthesized powders; however, pure β-SiAlON compacts were successfully obtained after SPS. The relative density of the products obtained by subjecting the combustion-synthesized powders to SPS was more than 99% of theoretical density.