Preparation and Structure of Silicon Oxycarbide Glasses Derived from Polysiloxane Precursors

Silicon oxycarbide phases with different O/Si ratios were prepared by pyrolysis of highly cross-linked polysiloxane precursors. Their structure was investigated using quantitative ²⁹ Si solid-state NMR and X-ray photoelectron spectroscopy (XPS). The prominent part played by the redistribution reactions on the ceramic yield, the composition of the oxycarbide phases and their structure was illustrated. In a large range of compositions the oxycarbide phases formed by pyrolysis at moderate temperature (<1000°C) may be described as a purely random arrangement of CSi₄ tetrahedra and Si–O–Si bridges.