Ferroelectric Ionic Molecular Crystals with Significant Plasticity and a Low Melting Point: High Performance in Hot‐Pressed Polycrystalline Plates and Melt‐Grown Crystalline Sheets

Abstract

Among ferroelectric crystals based on small molecules, plastic/ferroelectric crystals are currently receiving particular attention because they can be used as bulk polycrystals. Herein, we show that an ionic molecular ferroelectric crystal, guanidinium tetrafluoroborate, exhibits significant malleability and multiaxial ferroelectricity despite the absence of a plastic crystal phase. Powder samples of this crystal can be processed into transparent bulk crystalline plates either by pressforming or by melt-growing. The plates show high ferroelectric performance and related properties, demonstrating the largest hitherto reported spontaneous polarization for bulk polycrystals of small-moleculebased ferroelectrics. Owing to the ready availability of large-scale materials and processability into various bulk crystalline forms, this ferroelectric crystal represents a highly promising functional material that will boost research on diverse applications as bulk crystals.

Ionic plastic crystals and ionic liquids containing quaternary cations with alkenyl substituents: chemical phase transformations by bromine vapor

“…The melting entropies of plastic crystals are typically less than 21 J mol À1 K À1 . 4 Extensive studies on IPCs have been conducted on their solid-state properties such as ionic conductivity, [5][6][7][8] ferroelectricity, [9][10][11][12][13][14][15][16] magnetism, [17][18][19] and thermal energy storage. 20,21 In addition to quaternary salts, salts containing inorganic ions 22 and organometallic cations [23][24][25][26][27] also exhibit the IPC phase.…”

Mechanically deformable organic ferroelectric crystal with adaptive shape locking

“…Whereas, the new pursuits for more energy-saving, biocompatible, exible and wearable devices have driven great interest in molecular ferroelectrics over recent years, especially pure organic ones 10,11 . By taking the attributes of facile solution processing, lightweight, structural diversity and tunability, organic ferroelectric crystals also possess unrivalled advantages in material preparation and functional design [12][13][14][15] . Due to tight molecular packing or coordinated network, however, organic ferroelectrics usually exhibit low mechanical properties and inherent brittleness 16 , which are detrimental to their potential applications in exible electronics.…”

Organometallic Ionic Plastic Crystals Incorporating Cationic Half-Sandwich Complexes

“…Most of the salts displaying the IPC phase belong to the category of quaternary ammonium salts, which share structural similarities with ionic liquids. − Numerous studies have investigated molecular motion and phase transitions in these salts, with a particular focus on factors influencing the emergence of the IPC phase, including molecular shape and volumes. − IPCs have attracted attention owing to their high ionic conductivity − and their utility as solid electrolytes. Extensive research has explored their solid-state properties, encompassing areas such as ferroelectricity, ferroelasticity, piezoelectricity, − magnetism, − and heat storage properties. , …”