Statics and Dynamics of Ferroelectric Domains in Molecular Multiaxial Ferroelectric (Me3NOH)2[KCo(CN)6]

Abstract

The recent emergence of multiaxial molecular ferroelectrics opens up a new route toward technological evolution in the next-generation flexible/wearable device applications. However, a fundamental understanding of multiaxial ferroelectricity and polarization switching at the microscopic level in these materials is still missing. Herein, we study a high-temperature multiaxial perovskite ferroelectric (Me3NOH)2[KCo(CN)6] (TMC-4) that exhibits a bond-switching phase transition at 417 K with notable piezoelectricity and spontaneous polarization in the ferroelectric phase. The cleavage and reformation of coordination bonds and hydrogen bonds during the bond-switching transition all contribute to a large entropy change of 178.79 J K-1 kg-1 at the phase transition. Using piezoresponse force microscopy (PFM), we observed diverse ferroelectric domain structures and provide evidence for both 180° and non-180° domain switching and their possible effect on the functional properties of molecular ferroelectrics. The results provide an insight into the multiaxial ferroelectricity of TMC-4 at the microscopic level enabling its further use in device applications. © 2021 The Royal Society of Chemistry.