Fracture Toughness of a Partially Stabilized ZrO2 in the System CaO‐ZrO2

The room‐temperature fracture behavior of partially stabilized ZrO 3 (PSZ) in the system CaO‐ZrO 2 was investigated. Fracture energy was measured using standard single‐edge‐crack and work‐of‐fracture techniques. Attempts were made to relate the fracture toughness parameters to the microstructure of the material. Stable crack propagation was always observed; a model is proposed to explain these observations on the basis of the formation of a microcrack zone at the tip of a propagating crack. The occurrence of initial stable crack propagation is explained in terms of an increase in microcrack zone size. The possibility that crack stability results from testing geometry superimposed on the microcracking stability is also discussed.