MultipleFerroic Orderings in Lead-Free Hybrid MaterialInduced by Molecular Asymmetric Modification

The characteristics of multiple ferroic orderings can afford potential applications such as mechanical switches, energy conversion, and pressure sensors. However, it remains a tremendous challenge to achieve multiple ferroic orderings due to rigorous requirements for certain symmetry in the crystal lattice and symmetry breaking. The organic–inorganic halide material has been regarded as possessing great potential for ferroelectric and ferroelastic phase transition for its unique structures. Herein, by modifying molecular symmetries, we successfully obtained the lead-free hybrid halide material (AMP)₂SbBr₅ (AMP = 2-Amino-2-methyl-1-propanol). With the help of hydroxyl insertion, the mirror symmetry was broken, realizing ferroelectric and ferroelastic phase transitions. The lone-pair electron activity as well as the directional ordering of the organic cations triggered the saturated polarization of 11.28 μC cm^–2, which is the largest polarization ever found in antimony-based molecular ferroelectrics. This study enhanced lead-free molecular ferroelectric development and offers instructive inspiration for designing multiple ferroic orderings.