Thermodynamic Evaluation of the Si-C-Al-Y-O System for LPS-SiC Application

A thermodynamic dataset for the Si-C-Al-Y-O system was developed for calculations of heterogeneous phase equilibria and reactions in SiC-base engineering ceramics. The quinary system is of major interest for the understanding of the liquid phase sintering of silicon carbide ceramics using additives like alumina (Al(2)O(3)) and yttria (Y(2)O(3)). The thermodynamic dataset was developed by the CALPHAD method of thermodynamic optimization. Analytical descriptions for the Gibbs free energy functions of all phases in the Si-C-Al-Y-O system were assessed. The sublattice model using the compound energy formalism was used for the treatment of the solid phases. The liquid phase was described by using the partially ionic liquid model presented as (Al(3+), Si(4+), Y(3+))(P)(O(2-), SiO(4) (4-), Va, AlO(3/2), SiO(2), C)(Q), which covers metallic liquid and oxide liquid as a single phase.