Cost-effective synthesis of α-Si3N4 powders from recycled silicon waste

Silicon nitride (Si 3 N 4 ) with α -phase content ∼90.0 wt% and oxygen content ∼1.00 wt% was prepared by combustion synthesis method using recycled silicon waste from photovoltaic industry. The effects of reaction pressure and environmentally-friendly new additive C 3 H 6 N 6 on the phase composition, and morphology and reaction mechanism of the combustion synthesized α -Si 3 N 4 powder were studied. The results indicate that a lower N 2 pressure is conducive to increasing the α -phase content and reducing the oxygen content of the Si 3 N 4 powder. The addition of C 3 H 6 N 6 as an effective additive facilitates the deoxidation and nitridation reactions of recycled silicon waste, which further increases the α -phase content and reduces the oxygen content of the Si 3 N 4 powder. This work demonstrated that the recycled silicon waste from photovoltaic industry holds great promise to be used as the silicon source for the cost-effective synthesis of high quality α -Si 3 N 4 powder.