Fabrication of yttrium-stabilized a-SiAlON powders with rod-like crystals by combustion synthesis

Yttrium-stabilized a-SiAlON powders with rod-like crystals were fabricated by combustion synthesis. Effects of starting compositions including relative content of diluents on final phase assemblage and grain morphology of combustion products were discussed. With appropriate proportions of a-SiAlON seeds and NH4F additive, a-SiAlON powders with rod-like crystals could be fabricated. It was found that the addition of a-SiAlON and NH4F could improve the anisotropic growth of rod-like crystals. However, if too much NH4F was added, the phase purity of combustion products would be decreased obviously and more b-SiAlON was produced. Additionally, the as-synthesized a-SiAlON powders were heat treated at 1800 C for 1 h to examine their stability at the elevated temperature. The experimental results showed that after the heat treatment, single-phase a-SiAlON was obtained, revealing the high stability of combustion synthesized a-SiAlON powders.