Room Temperature Lead-Free Multiaxial Inorganic-Organic Hybrid Ferroelectric.

Abstract

In recent years, molecular ferroelectrics have received more and more attention. Nevertheless, the study of multiaxial molecular ferroelectrics is relatively rare, which significantly restricts the development of their applications in thin films and other potential fields. Here we demonstrate the characteristics of a room-temperature lead-free multiaxial inorganic-organic hybrid ferroelectric material [(CH3)2NH2] [C6H5CH2NH3]2BiBr6 (1), which goes through a distinctly reversible phase transition around 386 K and possesses six equivalent ferroelectric directions. At 330 K, the remnant polarization (Pr) of 1 is ∼1.0 μC·cm-2, and the coercive field (Ec) of 1 is 20 kV·cm-1. The multiaxial and switching polarization behaviors of 1 were declared with piezoresponse force microscopy (PFM). Notably, the emergence of six equivalent ferroelectric directions is induced by the easily disordered cations and highly geometrically symmetrical anions, because they usually lead to a large symmetry change in the order-disorder types of ferroelectrics. This work provides an effective approach to construct molecular multiaxial ferroelectrics.