FRACTURE BEHAVIOUR OF Si_3N_4-ZrO_2CERAMIC COMPOSITE

The fracture behaviour of tetragonal ZrO_2 toughened Si_3N_4 ceramic composite has been investigated using acoustic emission technique, X-ray diffraction, SEM and TEM. The results show that the fracture toughness increased markedly by addition of t-ZrO_2. The t-ZrO_2 particles show a considerable resistance to transformation. It is considered that the toughening mechanism of t-ZrO_2 addition might be crack deflection, crack branching and microcrack toughning.