Crack propagation in silicon nitride ceramics under various temperatures and grain boundary toughness

Crack deflection angles and fracture modes were investigated by elaborative observation of 5764 crack deflections, generated at 77 K, 159 K, 293 K and 500 K, in silicon nitride (Si3N4) ceramics. In addition, the effects of grain boundary toughness on crack propagation in Si3N4 ceramics were statistically analyzed based on a two-dimensional, polycrystalline model. The results demonstrated that temperature (77–500 K) had little influence on crack advance, but the change of grain boundary toughness contributed a lot to the change of crack propagation. The distribution of deflection angles varied distinctly and the fraction of transgranular fracture increased when the grain boundary toughness increased.