Stability of polarization vortices in PbTiO₃/SrTiO₃ superlattices under fracture

Abstract Artificial ferroelectric superlattices demonstrate exceptional piezoelectric and dielectric properties, which have garnered substantial research interest. Accurate characterization of these properties is indispensable for the application of ferroelectric superlattices. Since most ferroelectric materials are brittle, a comprehensive understanding of the fracture behavior is essential to ensure the reliability of superlattices. This study develops a coupled phase field model to simulate crack propagation with domain evolution in PbTiO 3 /SrTiO 3 superlattices. In this work, we examine the superlattice beam under three-point bending load. At the initial stage, a stable array of polarization vortices exists within the PbTiO 3 layers. Despite the occurrence of localized stretching, merging, or domain transformation of the polarization vortex near the crack tip, the polarization in PbTiO 3 gradually evolves back into a vortex array after the crack passes through. This process also contributes to a toughening effect, which delays crack propagation. This work contributes to the assessment of the structural reliability of ferroelectric devices for engineering applications.