Flexoelectric influence on crack propagation in ferroelectric single crystals: a phase-field approach

Ferroelectric materials, known for their inherent brittleness, are prone to brittle fracture. This limitation not only curtails the materials’ operational lifespan but also impinges on the reliability of the associated devices. Notably, the pronounced strain gradient present at the crack tip necessitates consideration of the flexoelectric effect—the interaction between strain gradient and electric polarization—in the fracture mechanics of ferroelectric materials. This study introduces a phase-field model incorporating the flexoelectric effect to elucidate its role on crack growth and domain evolution in ferroelectric single crystals. Our findings demonstrate that both crack trajectory and domain switching phenomena at the crack’s forefront are substantially influenced by the magnitude and sign of the flexoelectric coefficient, as well as the initial polarization direction. Depending on the computational scenarios, the flexoelectric effect can either exacerbate or impede crack propagation. Through meticulous examination of the mechanical field distributions and their temporal progression, we have uncovered the underlying mechanisms by which the flexoelectric effect governs crack propagation in ferroelectric single crystals. These insights pave the way for improving the fracture resistance and thereby enhancing the reliability of ferroelectric devices.