Synthesis of β-Si3N4 powder from quartz via carbothermal reduction nitridation

β-Si3N4 powder was synthesized via carbothermal reduction nitridation (CRN) method using quartz as starting material. The influence of synthesis temperature, C/SiO2 molar ratio and amount of Fe2O3 additive on the phase transformation and micro-morphology of β-Si3N4 powder was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The results showed that the optimal experimental conditions for the CRN synthesis of β-Si3N4 powder were 3 h sintering at 1600 °C in flowing nitrogen atmosphere with C/SiO2 molar ratio of 2.0 and amount of Fe2O3 additive of 5.0 wt.%. The prepared β-Si3N4 grains present a short hexagonal, rod-like morphology. Changes in experimental parameters affect the phase compositions and the morphology of the product. Excessive carbon promoted the formation reaction of β-SiC. Fe2O3 additive exerted a significant promotion on the formation of β-Si3N4 in CRN process by forming the low melting point eutectics.

Graphical abstractβ-Si3N4 powder was synthesized via carbothermal reduction nitridation method using quartz as starting material. The influence of synthesis temperature, C/SiO2 molar ratio and amount of Fe2O3 additive on the phase transformation and micro-morphology of β-Si3N4 powder was studied. The optimum parameters for controllable synthesis of low-cost β-Si3N4 powder were obtained.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► β-Si3N4 powder was prepared directly by CRN method from quartz. ► The optimum parameters for controllable synthesis of β-Si3N4 powder were obtained. ► Changes in process parameter affect phase compositions and morphology of products. ► The controllable synthesis method for β-Si3N4 can reduce the cost significantly.