Enhanced Electromechanical Response in 1D Hybrid Perovskites: Coexistence of Normal and Relaxor Ferroelectric Phases

Organic hybrid perovskites with polarization reversal are the emergent ferroelectric materials, lacking the connection between the domain-wall (DW) dynamics and the intrinsic microscopic polarization reversal. The polarization reversal experimentally and theoretically is investigated for normal and relaxor ferroelectrics coexisted in one-dimensional (1D) TMAPbI₃ (tetramethylammonium, TMA). Depolarization effects induce distinct DW dynamics in normal and relaxor ferroelectrics, leading to deviations in energy barriers between DW velocity models and theoretical predictions. In this research, it is found that the electric field-induced electromechanical response in relaxor ferroelectric raised by 124 times of d₃₃ from 0.29 pC N⁻¹ @ 0 kV cm⁻¹ to 37.17 pC N⁻¹ @ 2 kV cm⁻¹, which is 9 times higher than the value in normal ferroelectrics, implies an excellent electromechanical property in the relaxor ferroelectric. Phonon dispersions identify the soft ferroelectric mode, in which the asymmetric iodine displacements destroy the symmetry plane, ascribing the polarization reversal along the nonpolar axis and the strain- and field-enhanced electromechanical response in the relaxor ferroelectric. Through this research, the connection between the microscopic atomic motion, the macroscopic polarization reversal, and the depolarization effect is revealed, validating methods that are needed to develop the next generation of relaxor ferroelectrics.