Work

Molecular Symmetry and Geometry Engineering for High‐Temperature Ferroelectricity and Low Coercive Field in Hybrid Metal Halides

Year: 2025

Type: article

Abstract: Optimizing ferroelectric properties is critical for molecule‐based ferroelectrics toward practical applications, including enhanced saturation polarization ( P s ), elevated Curie temperature ( T C ), and reduced coercive field ( E c ). Recent advances in ferroelectrochemistry have provided efficient synthetic strategies to tailor these properties, with a focus on functionalizing organic components. However, the impact of combined molecular symmetry and geometry on ferroelectricity remains less understood. In this work, we construct a series of one‐dimensional ferroelectric hybrid metal halides (HMHs) using C 3v ‐symmetric trigonal pyramidal polar cations to systematically investigate how molecular symmetry and geometry modulate ferroelectric behavior. The model compound (TMS)PbI 3 (TMS = trimethylsulfonium) exhibits ferroelectricity up to its decomposition temperature (530 K), the highest among known HMH ferroelectrics, alongside an exceptionally low E c (0.25 kV cm −1 at 298 K). We demonstrate that the unique C 3v symmetry and trigonal pyramidal geometry of the TMS cation facilitate energy‐favorable uniaxial rotation about the polar 3‐fold axis and 90° polarity flipping during disordering in the ferroelectric–ferroelectric phase transition near 271 K. This partial disorder transition underpins the remarkable high‐temperature ferroelectric phase and low E c . Selenium‐ and phosphorus‐based analogs show similar properties with E c values of 0.55 and 0.47 kV cm −1 , respectively.

Source: Angewandte Chemie International Edition

DOI: 10.1002/anie.202523302