Effect of diluents and NH4F additive on the combustion synthesis of Yb α-SiAlON

In this paper, Yb α-SiAlON crystalline powders with elongated grains were prepared by combustion synthesis. The effects of diluents and NH4F additive on the phase composition and microstructure of combustion products were discussed in detail. It is found that proper diluents are helpful to weaken the agglomeration, improve the infiltration of N2, and hence facilitate the nitridation reaction. Single-phase α-SiAlON with elongated grains could be fabricated with advisable addition of diluents. Furthermore, adding proper amounts of NH4F additive was also beneficial to the nitridation of Si and the development of elongated grains. However, excessive addition of α-Si3N4 diluents or NH4F additive will result in β-SiAlON in final phase composition.