Effect of Additives on the Activation Energy for Sintering of Silicon Carbide

The combined‐stage sintering model was used to determine the activation energy, Q , of sintering for selected SiC‐based materials. SiC densified with a liquid (1.65 wt% Al) had an activation energy of 842±79 kJ/mol, a value between those for a silicon carbide densified with 1 wt% C and 0.25 wt% B 4 C ( Q =643±37 kJ/mol) and one densified with 2.5 wt% AlN ( Q =1022±122 kJ/mol), compositions which have no liquid phase below 1850°C. The SiC with Al additive began densification by 1500°C and the densification curve was offset by approximately 100°C compared with the other two materials below 1850°C. The choice and amount of additives not only affect densification and activation energy, but also influence microstructure and fracture mode, allowing engineering of mechanical properties.