Synthesis and Growth of 6H-SiC and 3C-SiC in an Al-Si-C System at 820 °C: Effect of the Reaction Path on the SiC Polytype

Many of the properties of SiC are decided by the polytype. In the present work, the effect of the reaction path on the SiC polytype is studied. Two kinds of SiC particles were prepared at 820 degrees C in an Al-Si-C system. Results show that 6H-SiC with a hexagonal structure and 3C-SiC with a face-centered cubic structure were obtained separately with a liquid-solid reaction and master alloy method. Further research revealed that 6H-SiC was formed via a one-step reaction with graphite as the precursor, while 3C-SiC was synthesized via a two-step reaction with Al4C3 as the intermediate product and precursor. A different reaction path and precursors result in a different growth process. 6H-SiC was grown under a polynuclear multilayer growth mechanism, while 3C-SiC was grown by a multiregion transition of Al4C3.