Recent advances in molecular ferroelectrics

Abstract

Due to their structural flexibility, tunability and easy processing, molecular ferroelectric materials have emerged to complement the well-known ferroelectric perovskite oxides. A number of compounds have been investigated but, with the exception of polymeric polyvinylidene fluoride, most have not succeeded in achieving their potential, mainly because of their poor ambient stability. It is only recently, with the surge of electronic type ferroelectricity, that molecular ferroelectrics with superior properties have been synthesized, making them competitive with respect to oxides. Nevertheless, the uniaxial nature of most of the compounds still represents the main bottleneck because it limits the transposition of the bulk properties into films. A possible solution is represented by the use of multiaxial molecular compounds or of low-dimensional systems. In this review, we highlight the main achievements in this field and summarize the open questions to be addressed if molecular ferroelectrics are to be exploited in devices.

Recent Advances in Organic and Organic–Inorganic Hybrid Materials for Piezoelectric Mechanical Energy Harvesting

“…[ 10 ] The 10 polar point groups [1 (C 1 ), 2 (C 2 ), m (C 1 h ) , mm2 (C 2 v) , 4 (C 4 ), 4mm (C 4 v ) , 3 (C 3 ), 3m (C 3 v ) , 6 (C 6 ), and 6mm (C 6 v ), with a unique polarization axis, whose spontaneous polarization varies with temperature, leading to pyroelectricity and the generation of charge in response to a temperature change. [ 11–13 ] If the intrinsic spontaneous polarization can be reversed or reoriented by an external electric field and produces a polarization reversal or hysteresis loop, the material exhibits ferroelectricity. Ferroelectric materials are a special type of dielectric material and a subgroup of both piezo‐ and pyroelectric materials.…”

A Biodegradable and Recyclable Piezoelectric Sensor Based on a Molecular Ferroelectric Embedded in a Bacterial Cellulose Hydrogel

“…Molecular ferroelectrics are a kind of inorganic−organic hybrid material that consists of inorganic atomic frameworks and organic molecular groups, whose spontaneous polarization originates from the asymmetry of lattices and/or relative displacement of polar groups. 30 With a wide range of applications, metal oxides such as single crystals and ceramics [e.g., lead zirconate titanate (PZT) and barium titanate (BTO)] and polymers such as poly(vinylidene fluoride) (PVDF) have dominated the ferroelectric field for a long time, even though the ferroelectric effect was first discovered in Rochelle salt, a typical molecular ferroelectric material. 31 Passion for molecular ferroelectrics has been reignited since the recent discovery of their high ferroelectric, piezoelectric, and pyroelectric performance.…”

“…For the purpose of realizing biodegradable and recyclable piezoelectric sensors, we infused molecular ferroelectrics into BC membranes. Molecular ferroelectrics are a kind of inorganic–organic hybrid material that consists of inorganic atomic frameworks and organic molecular groups, whose spontaneous polarization originates from the asymmetry of lattices and/or relative displacement of polar groups . With a wide range of applications, metal oxides such as single crystals and ceramics [ e.g.…”

Photoinduced Persistent Polarization Change in a Spin Transition Crystal

“…the generation of voltage and current in response to an electric field, mechanical stress, and temperature, respectively, which are widely used in applications such as energy harvesting, data storage media, capacitors, and sensors. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The polarization change in such materials is mainly caused by stimuli-dependent ion displacement, molecular order/ disorder, and electron transfer. Among the stimuli that can trigger polarization switching, light stands out because it provides a faster switching response and remote control.…”