Effect of Pore Size on Strength and Fracture Toughness of Zirconia Ceramics

The deformation behavior of ZrO₂ under compression of cylindrical and three point bending of V-notched beam-shaped samples has been investigated. The ceramics possess 50% porosity and the average pore size varying from 10 to 300 μm. It is shown that the formation of stochastic porosity and further increase in the average pore size lead to a multiple strength decrease relative to a non-porous sample. At the same time, the deformation behavior changes from elastic to pseudoplastic one reflected by the appearance of many local minima in the deformation curves and the increase in the relative ultimate strain. A plateau is found in the fracture toughness dependence on the pore size due to the increase in the main crack trajectory running mainly between the pores. In addition, the formation of multiple microcracks is found, also preventing the development of the main crack.