The Soft Molecular Polycrystalline Ferroelectric Realized by the Fluorination Effect.

TLDR: F fluorine substitution is applied to successfully design a multiaxial molecular ferroelectric, 3-fluoro-quinuclidinium perrhenate ([3-F-Q]ReO4), whose macroscopic ferro electricity can be realized in both powder compaction and thin-film forms, and makes it an ideal candidate for flexible and wearable devices, and biomechanical applications.

Abstract: For a century ferroelectricity has attracted widespread interest from science and industry Inorganic ferroelectric ceramics have dominated multibillion dollar industries of electronic ceramics, ranging from nonvolatile memories to piezoelectric sonar or ultrasonic transducers, whose polarization can be reoriented in multiple directions so that they can be used in the ceramic and thin-film forms However, the realization of macroscopic ferroelectricity in the polycrystalline form is challenging for molecular ferroelectrics In pursuit of low-cost, biocompatible, and mechanically flexible alternatives, the development of multiaxial molecular ferroelectrics is imminent Here, from quinuclidinium perrhenate, we applied fluorine substitution to successfully design a multiaxial molecular ferroelectric, 3-fluoroquinuclidinium perrhenate ([3-F-Q]ReO4), whose macroscopic ferroelectricity can be realized in both powder compaction and thin-film forms The fluorination effect not only increases the intrinsic polarization but also reduces the coercive field strength More importantly, it is also, as far as we know, the softest of all known molecular ferroelectrics, whose low Vickers hardness of 105 HV is comparable with that in poly(vinylidene difluoride) (PVDF) but almost 2 orders of magnitude lower than that in BaTiO3 These attributes make it an ideal candidate for flexible and wearable devices and biomechanical applications