Combustion synthesis and sintering of β-sialon ceramics (z = 2)

Abstract

Single-phase (β- SiAlON (Si4Al2O 2N6, z = 2) powder has been prepared by the combustion synthesis method. The raw materials (Si, Al and SiO2) were combusted with different ratios of (β-SiAlON (z = 1) diluent (0, 10, 20, 30, 40, 50 wt%) in 1 MPa of N2 pressure. Without diluent, the reaction temperature was very high (> 2000°C) and the product contained metal Si residue besides (β-SiAlON product. Both the reaction temperature and amount of residual Si decreased gradually with the increase of diluent content up to 50 wt%. At 50 wt% dilution, the combustion temperature was 1859°C and the XRD analysis showed complete conversion to pure (ß- SiAlON (z = 2). The individual peaks of (β-SiAlON (z = 1) diluent were also detected in the XRD patterns and disappeared after using the product itself as a diluent five time repeats of combustion at which single-phase (β-SiAlON (z = 2) was produced. The sinterability of the best synthesized powder was further studied by spark plasma sintering (SPS) with 5wt% Y2O3 as a sintering aid. High densification (∼97.3%) was obtained after sintering at 1600°C for 5 min under 30MPa pressure with heating and cooling rates of 100°C/min. The Vickers hardness and fracture toughness of the sintered SiAlON were 14.8GPa and 4.4MPam1/2, respectively. © 2008 The Society of Materials Science,.