Fabrication of mixed α/β-SiAlON powders via salt-assisted combustion synthesis

• Y- and Ca-α/β-SiAlON and α-SiAlON were synthesized via salt-assisted combustion synthesis.
• The α/β ratios and the morphology of the product were affected by the type of metal chlorides.
• The use of NaCl affording high α/β ratios and equiaxed morphologies.
• The use of MgCl2 resulting in low α/β ratios and elongated grains.

High-quality Y- and Ca-α/β-SiAlON and α-SiAlON ceramics were synthesized via salt-assisted combustion synthesis from Si, Al, and metal oxide (Y2O3 and CaO) with the addition of NaCl and MgCl2 under a nitrogen pressure of 1 MPa. NaCl and MgCl2 were employed as they act as excellent diluents that effectively absorb the reaction heat through melting and evaporation. We found that the type of metal chlorides employed significantly affected the α/β ratio and the morphology of the product, with the use of NaCl affording high α/β ratios and equiaxed morphologies, while the use of MgCl2 resulting in low α/β ratios and elongated grains. The results of this work suggest that high-purity α/β-SiAlON composite products of intended α/β ratios can be successfully fabricated by controlling the initial metal chloride content.