Ferroelectricity and Piezoelectricity in Free-Standing Polycrystalline Films of Plastic Crystals
Ferroelectricity and Piezoelectricity in Free-Standing Polycrystalline Films of Plastic Crystals
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DOI：
10.1021/jacs.7b10539
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发表时间：
2018-01-10
影响因子：
15
通讯作者：
Inabe, Tamotsu
中科院分区：
文献类型：
--
作者：
Harada, Jun;Yoneyama, Naho;Inabe, Tamotsu
塑料晶体代表了一种独特的化合物类别，经常在具有球形结构的分子中遇到。塑料晶体高度对称的立方晶体结构使这些材料具有多轴铁电性，使得晶体极化轴的三维重新排列成为可能，这是传统的低晶体对称性分子铁电晶体所无法实现的。在这项工作中，我们将注意力集中在塑性晶体的另一个特征上。我们合成了新的塑料/铁电离子晶体四甲基四氯铁酸铵（III）和四甲基溴三氯铁酸铵（III），并发现通过压制这些化合物的粉末样品可以很容易地制备出独立的半透明薄膜。由此获得的多晶薄膜在室温下表现出铁电极化开关和相对较大的压电响应。功能薄膜的现成可用性证明了这种塑料/铁电晶体的实际用途，并且考虑到各种可能的组成阳离子和阴离子，这些独特而有吸引力的功能材料应该有广泛的应用。
Plastic crystals represent a unique compound class that is often encountered in molecules with globular structures. The highly symmetric cubic crystal structure of plastic crystals endows these materials with multiaxial ferroelectricity that allows a three-dimensional realignment of the polarization axes of the crystals, which cannot be achieved using conventional molecular ferroelectric crystals with low crystal symmetry. In this work, we focused our attention on malleability as another characteristic feature of plastic crystals. We have synthesized the new plastic/ferroelectric ionic crystals tetramethylammonium tetrachloroferrate(III) and tetramethy-lammonium bromotrichloroferrate(III), and discovered that free-standing translucent films can be easily prepared by pressing powdered samples of these compounds. The thus obtained polycrystalline films exhibit ferroelectric polarization switching and a relatively large piezoelectric response at room temperature. The ready availability of functional films demonstrates the practical utility of such plastic/ferroelectric crystals, and considering the vast variety of possible constituent cations and anions, a wide range of applications should be expected for these unique and attractive functional materials.