Study of the pyrolysis process of an hybrid CH3SiO1.5 gel into a SiCO glass

Silicon oxycarbide samples were prepared by polymer pyrolysis using a methyltriethoxysilane-derived precursor. Transparent crack-free gel samples were obtained from the alkoxide by the sol–gel process. The dried gel samples were pyrolysed at different temperatures in the range between 400 and 1500 °C in Ar atmosphere. The chemical and microstructural evolution during pyrolysis were followed by FT-IR absorption, Raman scattering and photoluminescence (PL).The FT-IR spectra show the change in Si–O–Si asymmetric stretching, C–Hx, Si–CH3 stretching vibrational bands. The peak position and shape of these bands were found stable up to 600 °C. Above this temperature, a remarkable change in shape and peak position of Si–O–Si related vibration, reduction in C–Hx and Si–CH3 stretching absorption bands have been observed. Degradation of Si–CH3 and the simultaneous formation of Si–CH2–Si via Si–CH2–CH2–Si is explicitly observed, experimentally. Annealing the sample at 800 °C starts to show the clear presence of D and G bands, related to the free carbon precipitation and its segregation with the temperature. The broad PL spectra centered at around 670 nm for the samples pyrolysed at 1500 °C shows an important information regarding the presence of crystalline SiC.