Room-Temperature Ferroelectricity and Gigantic Dielectric Susceptibility on a Supramolecular Architecture of Phenazine and Deuterated Chloranilic Acid

Ferroelectricity and large dielectric constant at room temperature have been demonstrated for cocrystals of phenazine and anilic acids constructing supramolecular assemblies. Deuteration of the anilic acids gives rise to an increase by more than 50 K in the transition temperature, which exceeds room temperature for the deuterated chloranilic acid. At room temperature in air, the crystals show a clear polarization hysteresis with a small coercive field. Application of hydrostatic pressure and halogen substitution in the anilic acids bring about the structural effect on the transition temperature in a parallel way, whereas the deuterium substitution does this in a distinct way. The observed large deuteration effect cannot be elucidated by the geometric change of the hydrogen bond, which has been considered as the possible mechanism of ferroelectricity in the conventional hydrogen-bonded with double-well potential.

本研究证实，由吩嗪（phenazine）与苯胺酸（anilic acids）构筑超分子组装体（supramolecular assemblies）形成的共晶（cocrystals），在室温下可表现出铁电性（ferroelectricity）与大介电常数（dielectric constant）。对苯胺酸进行氘代（deuteration）处理后，其相变温度（transition temperature）可提升超过50 K，其中氘代氯冉酸（chloranilic acid）的相变温度已超过室温。在室温空气环境中，该类晶体呈现出清晰的极化迟滞回线，且矫顽场（coercive field）较小。施加静水压（hydrostatic pressure）与在苯胺酸分子中引入卤素取代（halogen substitution），均可通过结构效应以相似的路径调控相变温度；而氘取代的调控机制则截然不同。观测到的显著氘代效应无法通过氢键（hydrogen bond）的几何变化予以解释，而在传统的具有双阱势（double-well potential）的氢键型铁电体系中，氢键的几何变化曾被视作铁电性的潜在起源机制。