Formation of silicon nitride from silica

The formation of Si3N4, during the carbothermic reduction of SiO2 in the presence of small Fe additions combined with nitridation is a complex process involving several solid-solid, gas-solid, gas-liquid-solid, and gas-gas reaction stages. The catalytic action of iron manifests itself in the formation of an intermediate compound — iron carbosilicide. The product of the nitridation of FeSixCy isα-Si3N4, and that of the nitridation of silicon, β-Si3N4.