A Molecular Polycrystalline Ferroelectric with Record‐High Phase Transition Temperature

Abstract

An outstanding advantage of inorganic ceramic ferroelectrics is their usability in the polycrystalline ceramic or thin film forms, which has dominated applications in the ferroelectric, dielectric, and piezoelectric fields. Although the history of ferroelectrics began with the molecular ferroelectric Rochelle salt in 1921, so far there have been very few molecular ferroelectrics, with lightweight, flexible, low-cost, and biocompatible superior properties compared to inorganic ceramic ferroelectrics, that can be applied in the polycrystalline form. Here, a multiaxial molecular ferroelectric, guanidinium perchlorate ([C(NH ) ]ClO ), with a record-high phase transition temperature of 454 K is presented. It is the rectangular polarization-electric field (P-E) hysteresis loops recorded on the powder and thin film samples (with respective large P of 5.1 and 8.1 µC cm ) that confirm the ferroelectricity of [C(NH ) ]ClO in the polycrystalline states. Intriguingly, after poling, the piezoelectric coefficient (d ) of the powder sample shows a significant increase from 0 to 10 pC N , comparable to that of LiNbO single crystal (8 pC N ). This is the first time that such a phenomenon has been observed in molecular ferroelectrics, indicating the great potential of molecular ferroelectrics being used in the polycrystalline form like inorganic ferroelectrics, as well as being viable alternatives or supplements to conventional ceramic ferroelectrics.

Piezoelectric Energy Harvesting Based on Multiaxial Ferroelectrics by Precise Molecular Design

“…[17][18][19] Multiaxial ferroelectrics with multiple equivalent polarization directions are highly preferred for such applications because more equivalent ferroelectric axes allow random spontaneous polarization vectors to be oriented along the electric field to achieve reversible switching between multiple directions, and the piezoelectric effects can also occur in multiple directions to produce optimal performance. [20][21][22][23][24] Most ceramic ferroelectrics have no more than three equivalent…”

Ferroelectric Metal–Organic Framework as a Host Material for Sulfur to Alleviate the Shuttle Effect of Lithium–Sulfur Battery

“…[9][10][11] Ferroelectric materials usually exhibit excellent ferroelectric, piezoelectric, ferroelastic and other distinctivep hysicalp roperties, such as colossal magnetoresistancea nd high dielectric constant properties, etc.,w hich can be widely used as photoelectric and energy storage devices. [12][13][14] Among these attractive properties, the spontaneousp olarizations witching behavior of ferroelectrics under the irritation of an externale lectric field is extremely important in theoretical research and application fields. [15] Recently,t he ceramic ferroelectric has been used as additives to sulfurc athodes becauseo ft he internal electric field inducedb ys pontaneous polarization to trap polysulfides.…”

Ferroelectric Behavior of an Octahedral Metal‐Ligand Cage and Its 2D‐Connected Cage Framework

“…Such increments in P r may be attributed to the alignment of some randomly oriented domains with rising temperature. [34] With further increase in temperature, crystals develop cracks and loss of crystallinity. For 2, such measurements gave inconsistent values probably due to the random loss of solvates upon heating the sample.…”