Effect of NH4Cl addition on the morphology of β-SiAlON powders prepared by salt-assisted nitridation

A novel method of fabricating β-SiAlON powders by salt-assisted nitridation using NaCl and NaF as the molten salt medium is proposed. The salt-assisted nitridation synthesis was carried out with Al, Si, and SiO2 powders, fixed amounts of NaCl and NaF, and varying amounts NH4Cl, which was used as an auxiliary nitrogen source. The phase compositions and particle morphologies of the synthesized powders were analyzed. The results demonstrated that, as the NH4Cl content increased, the amount of β-SiAlON crystals increased, and the morphologies of the β-SiAlON crystals became rod-like with smooth tops and conical tips at 1350°C. As the temperature increased, β-SiAlON crystals became rod-like with smooth tops. In addition, the z-values of β-SiAlON were different when different amounts of NH4Cl were added. These results indicate that NH4Cl serves as a nitrogen source; varying the NH4Cl content can limit the growth of β-SiAlON crystals.