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 degrees 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-H-x, Si-CH3 stretching vibrational bands. The peak position and shape of these bands were found stable up to 600 degrees C. Above this temperature, a remarkable change in shape and peak position of Si-O-Si related vibration, reduction in C-R, 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 degrees 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 degrees C shows an important information regarding the presence of crystalline SiC. (C) 2007 Elsevier B.V. All rights reserved.