High‐Temperature and Large‐Polarization Ferroelectric with Second Harmonic Generation Response in a Novel Crown Ether Clathrate

• Published in: Chemistry : a European journal Vol. 27; no. 54; pp. 13575 - 13581
• Main Authors: Han, Ding Chong, Tan, Yu Hui, Li, Yu Kong, Wen, Jia Hui, Tang, Yun Zhi, Wei, Wen Juan, Du, Peng Kang, Zhang, Hao
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 24.09.2021
• Subjects: Calorimetry; Chemistry; Clathrates; Crown ethers; Crystals; dielectric anomalies; Differential scanning calorimetry; Ferroelectric materials; ferroelectric properties; Ferroelectricity; Harmonic response; high-temperature reversible phase transition; Hysteresis; Hysteresis loops; Optical materials; Optical properties; Optics; Phase transitions; Physical properties; Polarization; Room temperature; Second harmonic generation; SHG response; Temperature dependence
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202101707

Molecular ferroelectrics of high‐temperature reversible phase transitions are very rare and have attracted increasing attention in recent years. In this paper is described the successful synthesis of a novel high‐temperature host‐guest inclusion ferroelectric: [(C6H5NF3)(18‐crown‐6)][BF4] (1) that shows a pair of reversible peaks at 348 K (heating) and 331 K (cooling) with a heat hysteresis about 17 K by differential scanning calorimetry measurements, thus indicating that 1 undergoes a reversible structural phase transition. Variable‐temperature PXRD and temperature‐dependent dielectric measurements further prove the phase‐transition behavior of 1. The second harmonic response demonstrates that 1 belongs to a non‐centrosymmetric space group at room temperature and is a good nonlinear optical material. In its semiconducting properties, 1 shows a wide optical band gap of about 4.43 eV that comes chiefly from the C, H and O atoms of the crystals. In particular, the ferroelectric measurements of 1 exhibit a typical polarization‐electric hysteresis loop with a large spontaneous polarization (Ps) of about 4.06 μC/cm2. This finding offers an alternative pathway for designing new ferroelectric‐dielectric and nonlinear optical materials and related physical properties in organic‐inorganic and other hybrid crystals. A modern material: A novel high‐temperature host‐guest inclusion ferroelectric, [(C6H5NF3)(18‐crown‐6)][BF4], has successfully been synthesized; it underwent a reversible structural phase transition around Tc=348 K, with a wide band gap of 4.43 eV. The chief contributors to this are the C, H and O atoms of the crystals, the obvious second harmonic generation response and the large value of spontaneous ferroelectric polarization of around 4.06 μC/cm2.