Crystallization of Amorphous SiCN Ceramic Annealed in Vacuum

SiCN ceramic was fabricated by electro-thermal pyrolysis using hexamethyldisilazane as precursor. X-ray diffraction and transmission electron microscope were employed to study crystallization process of amorphous SiCN after annealing at temperature from 1700℃ to 1900℃ in vacuum. Decomposition-crystallization mechanism was used to characterize its crystallization process. Amorphous SiCN begin to decompose below 1300℃ in vacuum and Si-C-enriched districts are formed and then changes to form β-SiC crystal. Crystallinity degree increases as treated temperature rises. Phase transition from β-SiC to α-SiC occurs after annealing at 1700℃. The nitrogen is released in the form of N2 and Si3N4 crystal is not detected though it often exists in the SiCN annealed in N2 atmosphere.