Crystallization behavior of amorphous silicon carbonitride ceramics derived from organometallic precursors

The crystallization behavior of organometallic-precursor-derived amorphous Si-C-N ceramics was investigated under N-2 atmosphere using X-ray diffractometry (XRD), transmission electron microscopy (TEM), and solid-state Si-29 nuclear magnetic resonance (NMR) spectroscopy. Amorphous Si-C-N ceramics with a C/Si atomic ratio in the range of 0.34-1.13 were prepared using polycarbosilane-polysilazane blends, single-source polysilazanes, and single-source polysilylcarbo-diimides. The XRD study indicated that the crystallization temperature of Si3N4 increased consistently with the C/Si atomic ratio and reached 1500 degreesC at C/Si atomic ratios ranging from 0.53 to 1.13. This temperature was 300 degreesC higher than that of the carbon-free amorphous Si-N material. In contrast, the SiC crystallization temperature showed no clear relation with the C/Si atomic ratio. The TEM and NMR analyses revealed that the crystallization of amorphous Si-C-N was governed by carbon content, chemical homogeneity, and molecular structure of the amorphous Si-C-N network.