Direct observation of domain switching and crack nucleation in a piezoelectric material

The effect of an electric field on domain switching and fatigue induced crack nucleation and growth in a piezoelectric material of nominal composition Pb(Zr0.5, Ti0.5)O3 has been investigated. The ceramic was subjected to localised static and cyclic electric fields, which were applied via pairs of closely spaced surface-mounted electrodes, while simultaneously imaging the microstructure in the SEM. Electric field–polarisation hysteresis loops were also collected from the local region using the same electrodes.Domain wall mobility was observed above a threshold electric field strength, as was microcracking. Cracks were seen to nucleate at grain boundaries, and were sometimes associated with microstructural features, such as pores. Crack propagation was mainly intergranular, and occurred preferentially in a direction parallel to the local field direction. Transgranular fracture was also observed, with the crack path being influenced by interaction with domain boundaries. Factors affecting domain switching and crack propagation are discussed in the context of the locally applied electric field.