Atomic-scale Structure of Polymer-route Si-C-O Fibers Observed by Synchrotron Radiation X-ray Diffraction

摘要

The atomic scale structure of amorphous Si-C-0 ceramics fibers produced from the pyrolysis of a polycarbosilane precursor has been investigated by X-ray diffraction using high-energy synchrotron radiation at SPring-8. First peak in the total correlation function T(r) of the amorphous and the heat-treated fibers is analyzed to consist of two contributions: Si-C (1.89 A) and Si-O (1.61 A) bonds. The coordination number of C and/or O around Si is about four. This suggests that the Si-C-O fibers basically have a network structure that consists of two tetrahedral units: SiC_4 and SiO_4. The local chemical and structural orders vary continuously in the materials from the disordered network structure of SiC_4 and SiO_4 tetrahedra (mixture of amorphous SiC and SiO_2) to nanocrystals of SiC and SiO_2, through the ternary Si-C-O solid solution which is believed to have an intermediate structure between the amorphous and crystalline states.