High-Temperature Metal-Free Molecular Ferroelectrics with Large Spontaneous Polarization,Inorganic Chemistry

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High-Temperature Metal-Free Molecular Ferroelectrics with Large Spontaneous Polarization
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2023-05-31 , DOI: 10.1021/acs.inorgchem.3c00998
Yan-Xin Zhao ₁ , Kai-Ge Gao ₂ , Zi-Shuo Yao ₁ , Jun Tao ₁

Affiliation

In the past two decades, numerous molecular ferroelectrics have been reported. However, metal-free molecular ferroelectrics with high working temperatures and large spontaneous polarizations are still uncommon. Herein, we present two metal-free molecular ferroelectrics prepared from monoprotonated hexamethylenetetramine (HMTA), namely (HMTAH)Cl and (HMTAH)Br, which crystallize in a polar point group of 3m. In these crystals, the polar HMTAH⁺ organic cations can be reoriented 180° along the polar axis because of the quasispherical molecular geometry. As a result of the large shift of the positively charged protonated N atoms, these compounds demonstrate large spontaneous polarizations with values of 8.3 and 8.1 μC cm^–2 and high working temperatures of 390 and 435 K, respectively. The ferroelectric property of these compounds is characterized with second-harmonic generation, ferroelectric hysteresis loop, and pyroelectric current measurements.

中文翻译：

具有大自发极化的高温无金属分子铁电体

在过去的二十年中，已经报道了许多分子铁电体。然而，具有高工作温度和大自发极化的无金属分子铁电体仍然不常见。在此，我们提出了两种由单质子化六亚甲基四胺 (HMTA) 制备的无金属分子铁电体，即 (HMTAH)Cl 和 (HMTAH)Br，它们在 3 m的极点群中结晶。在这些晶体中，由于准球形分子几何结构，极性 HMTAH ⁺有机阳离子可以沿极轴重新定向 180°。由于带正电的质子化 N 原子发生大位移，这些化合物表现出较大的自发极化，值为 8.3 和 8.1 μC cm ^–2工作温度分别为 390 和 435 K。这些化合物的铁电特性通过二次谐波产生、铁电磁滞回线和热释电电流测量来表征。

更新日期：2023-05-31

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