Effect of seeding and carbon content on the formation and microstructure of Ca-α-SiAlON

Abstract

Ca-α-SiAlON powder was synthesized by carbothermal reduction nitridation process at a low temperature (i.e., 1400 °C, 2 h). The precursor was prepared by a novel sol-gel process. The effect of carbon content and seeding on the microstructure and purity of the Ca-α-SiAlON powder was investigated by X-ray diffraction and scanning electron microscopy. It was found that carbon, in addition to reduction the raw materials, preventing agglomeration of the final product via its steric hindrance. There was an optimal amount of carbon in the precursor and an excessive increase in that caused impurities such as AlN would increase again in the final product, which could be due to an increase in the diffusion distance of the reagents. The results showed that in some cases Ca-α-SiAlON with a distribution of X-values is formed by different reaction path. Seeding has an effective role in the purity and morphology of the products, and single phase Ca-α-SiAlON powder was prepared with the addition of 2 wt% Ca-α-SiAlON seed to the precursor at 1530 °C for 2 h.