Toughening of ferroelectric ceramics under polarization switching

For ferroelectric ceramics under coupled mechanical and electrical loading, the intensified stress and electric fields in the vicinity of a crack tip lead to domain switching. The switched domain induces incompatible strain, and consequently changes the apparent fracture toughness. In this paper, the toughness variation induced by domain switching is analysed via a domain switching strip model. A local energy release rate at the crack tip is used to evaluate toughening and weakening in ferroelectric ceramics induced by domain switching. It is shown that the crack growth can be either enhanced or retarded depending on the magnitude, the direction, and type of the applied electrical load. The prediction based on the present model explains the conflicting experimental data on toughness variations with respect to the applied electric field. It is also shown that a substantial enhancement in toughness is possible due to domain switching, and domain switching in the field of a crack tip provides the requisite energy absorption mechanism for enhancement of fracture toughness.