Metal oxide additives for the sintering of silicon carbide: Reactivity and densification

The effectiveness of sintering additives for β-SiC was examined based on thermodynamic calculations and experimental observations under hot pressing conditions of 1700–1800 °C. Various types of oxides, such as Al2O3, Fe2O3, MgO, TiO2, WO3 and Y2O3, were examined theoretically by considering the Gibbs formation free energy and vapor pressure. According to experimental observations expanded to their binary and ternary systems after hot pressing at 1750 °C and 20 MPa, Al2O3, MgO, Y2O3 and their mixed systems were found to be the only effective sintering additives that do not react with β-SiC at high temperatures. On the other hand, Fe2O3, TiO2, WO3 and their combinations with other oxides were not effective because of the reaction with β-SiC by forming the corresponding metal carbides and/or silicides, as predicted by thermodynamic simulations. Moreover, the experimental results for the additional possible components were also included.

► Examining effective sintering additives for β-SiC based on thermodynamic calculations and experimental observations.
► Finding Al2O3, MgO, Y2O3 and their mixed systems as effective sintering additives for β-SiC.
► Proving the importance of stability without decomposing β-SiC at hot pressing condition to be an effective sintering additive.
► Proving the usefulness of thermodynamic approach in selecting the effective sintering additives for β-SiC.