Phase-field simulation of domain switching in ferroelectric trilayer films under bending-induced strain gradient

Abstract: Flexible ferroelectrics possess significant potential for wearable electronics and bio-inspired devices, yet their electromechanical coupling mechanisms under dynamic bending remain elusive. This study employs phase-field simulations to investigate the effects of bending deformation on domain structures and macroscopic ferroelectric responses in (SrTiO3)10/(PbTiO3)10/(SrTiO3)10 trilayer films. By constructing computational models for upward-concave (U-shaped) and downward-concave (N-shaped) configurations, we analyze the regulation of polarization patterns by strain distributions under varying curvature radii. The results demonstrate that the two bending modes generate opposite through-thickness strain gradients: U-shaped bending produces compressive strain in the upper layer and tensile strain in the lower, while N-shaped bending yields the reverse. These inhomogeneous strains drive distinct polarization reconfigurations within the PTO layer. While stable vortex-antivortex pairs persist at moderate curvatures, reducing the bending radius triggers divergent topological transitions -- U-shaped bending transforms vortex pairs into zigzag-like domains, whereas N-shaped bending promotes out-of-plane c-domain evolution. Crucially, bending-induced strain gradients generate transverse flexoelectric fields that markedly modulate hysteresis loops. U-shaped bending introduces a negative flexoelectric field, shifting loops rightward and suppressing maximum polarization Pmax. In contrast, N-shaped bending generates a positive field, shifting loops leftward and enhancing Pmax. Furthermore, analysis of polarization switching reveals that bending mediates domain-evolution pathways and reversal dynamics.