New paradigm of a metastable phase diagram presenting structural transformations induced by annealing of Si-C-N amorphous ceramics derived from polymer precursors

摘要

Amorphous Si-C-N domains, nanocrystalline SiC and nanocrystalline Si{sub}3N{sub}4 identified in the structure of Si-C-N polymer derived ceramics (SiCN PDCs) have been proposed as metastable phases am-SICN, NASIC and NASIN. To study structural transformations of SiCN PDCs, the thermodynamic equilibria of these phases have been computed using previously derived Gibbs energies G(am-SICN), G(NASIC) and G(NASIN). The computational results are presented in the form of metastable phase diagrams. A new paradigm of these diagrams is explained as due to time dependence implemented into the Gibbs energies G(NASIC) and G(NASIN) and the application to interpretation of the crystallization course observed for SiCN PDCs is discussed.