Rapid crystallization of amorphous silicon nitride powder accelerated by liquid Si

The complete crystallization time of amorphous silicon nitride powder could be reduced from more than 6 h to 30 min by adding Si powder in N2 atmosphere. The crystallization process may be affected by the synergy of the reaction between Si and N2 and the liquid phase of Si due to the addition of Si. The α-Si3N4 produced by the added Si and nitrogen may be the seed of the crystallization process. The amorphous silicon nitride powder may be dissolved in the liquid phase and then precipitated as α-Si3N4. This article uses Ar instead of N2 to shield the reaction between Si and N2 in order to analyze the role of the two mechanisms. The added Si powder accelerates the crystallization process effectively in Ar. Powder of more than 70% crystalline phase content is produced by adding 5% Si annealing at 1400 °C for 15 min. The existence of liquid Si is the key factor to promote the crystallization process and the process follows the solution–precipitation mechanism. The final products are mainly α-Si3N4 and Si2N2O. The SEM results show that most of the products are irregular rod-like particles.