Influence of NH 4 F additive on the combustion synthesis of β-SiAlON in air

Abstract The preparation of β-SiAlON, Si 6– z Al z O z N 8– z ( z = 1–4), was investigated using the combustion synthesis (CS) technique with Si, Al, and CO(NH 2 ) 2 as the main raw materials in air. Different amounts of NH 4 F were used as a low-melt additive to the raw materials to decrease the reaction temperature and promote β-SiAlON formation. Phase and microstructural analyses of the reaction products were performed by X-Ray diffraction (XRD) and FE-SEM/energy dispersive X-ray spectrometer techniques. FT-IR spectroscopy was also used to demonstrate the formation of β-SiAlON in the final product. The phase and microstructural analysis results showed that NH 4 F addition improved the exothermic reaction of β-SiAlON phase formation and increased its content in the final synthesized powders. Additional heat treatment of the sample at the optimum z -value ( z = 4) and different percentages of NH 4 F revealed the positive effect of the low-melt additive on β-SiAlON phase formation under very low N 2 pressure.