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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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