Mechanical properties and fracture behaviour of ZrO2-Y2O3 ceramics

Stabilized ZrO₂-Y₂O₃ ceramics have been prepared with varying grain sizes and microstructures with the help of different preparation techniques. Bi₂O₃ has been added as a sinter aid to some of the samples. This results in a certain amount of a zirconia-rich second phase. For Bi₂O₃-free samples the fracture toughness (K_lc), and therefore the fracture energy, increases with decreasing grain size. A linear relation with the inverse square root of the average grain size is found. The highest value ofK_lc amounts to 4.1 MPa m^1/2. Fracture toughness values of 1.9±0.2 MPa m^1/2 are measured for Bi₂O₃ containing materials. The fracture surfaces are intergrannular for Bi₂O₃-containing and transgranular for Bi₂O₃-free samples, respectively.