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

Abstract

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.