Fracture toughness of alumina and ZTA ceramics: microstructural coarsening effects

The influence of zirconia particles addition and microstructural coarsening, as a result of different heat treatments, on the fracture toughness of a monolithic alumina and a zirconia-toughened-alumina (ZTA) composite is studied. It is observed that addition of zirconia particles results in an enhancement of fracture toughness with respect to that exhibited by the alumina matrix. Similarly, microstructural coarsening within ZTA is found to produce a fracture toughness increment, mainly associated with the effect of zirconia particle size on their phase transformability. The obtained mechanical properties and grain growth kinetics are discussed in terms of microstructural features and operative toughening mechanisms.