Domain evolution, dielectric and piezoelectric response in bent freestanding PbTiO₃ ferroelectric nanowires

Ferroelectric oxides with excellent flexibility are of significant practical and theoretical interests in recent studies. With most up-to-date research efforts, the effect of large bending on properties of nano-scale ferroelectric materials is still to be investigated. In this work, we elucidate the effect of bending angle on ferroelectric domain structures and material properties of bending PbTiO₃ nanowires using phase-field simulations and thermodynamic modeling. We find non-monotonic dependencies of the coercive fields, dielectric responses and piezoelectric properties on the bending angle. A maximum enhancement of 462 % and 226 % in the dielectric constant and piezoelectric coefficient, respectively, is achieved at an 18° bending angle for the PbTiO₃ nanowire with a radius of R=10nm and length L=100nm, which is attributed to the formation of strong-response zones within the nanowire as illustrated by both the phase-field and thermodynamic analysis. The current work provides useful theoretical insights for the experimental explorations into ferroelectric functionalities of nanomaterials and potential applications of high-performance flexible ferroelectric-based nanodevices.