Fracture tests on poled and depoled lead zirconate titanate (PZT) ceramics indicate that purely electric fields are able to propagate the conductive cracks (notches) and fracture the samples. To understand the fracture behavior of conducting cracks in ferroelectric ceramics, an electric dipole model is proposed, in which a discrete electric dipole is used to represent the local spontaneous polarization and the force couples are used to represent the local strains. The electric dipole model provides basic solutions for microstructural modeling. The microstructural modeling is based on a domain switching mechanism. The domain structure is simulated with a grid of points where polarizations and strains vary with the applied loads. As a first step study, the microstructural modeling is conducted for a dielectric material with a conductive crack. The simulation result explains why the electric fracture toughness is much higher than the mechanical fracture toughness.
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