Thermodynamic description of the Dy-Si-C system in silicon carbide ceramics

To predict the thermal behaviors of Dy3Si2C2 during sintering or joining process of the silicon carbide (SiC) ceramics, we established a detailed thermodynamic description of Dy-Si-C by coupling the first-principles calculations and the CALPHAD (CALculation of PHAse Diagram) approach. First-principles calculations were applied to acquire the formation enthalpies of key compounds, which can perform as end-members during optimization. We proposed a first Dy-C binary phase diagram referred to other RE-C (RE = La, Ce and Pr) systems. The Dy-Si system, previously described with the modified quasichemical model (MQM), was modeled based on the random-mixing Bragg Williams model in this work. The presently obtained thermodynamic parameters can reasonably reproduce the available experimental data and elucidate the thermal behaviors of Dy3Si2C2. We calculated that Dy3Si2C2 reacted with SiC via ternary eutectic reaction at 1432 degrees C, which was consistent with the reported experimental results. Further work of other SiC-based systems may provide foresight to explore new sintering aids in ceramics.