New Molecular Ferroelectrics Accompanied by Ultrahigh Second-Harmonic Generation

Abstract

Second-harmonic generation (SHG) is one of the outstanding properties for practical applications. However, the great majority of molecular ferroelectric materials have very low nonlinear optical coefficients, attenuating their attractive performance. Here we synthesized (4-amino-2-bromopyridinium)(4-amino-2-bromopyridine)tetrafluoroborate (1), whose second-order nonlinear optical coefficient reaches up to 2.56 pm V(-1), 2.67 times of that of KDP, and (4-amino-2-bromopyridinium)tetrafluoroborate (2), possessing a more incredible large second-order nonlinear optical coefficient as high as 10.24 pm V(-1), 10.67 times that of KDP. The compound 1 undergoes two reversible phase transitions at around T1 = 244.1 K and T2 = 154.6 K, caused by dramatic changes of the protonated cations and order-disorder of anions, which was disclosed by differential scanning calorimetry, heat capacity, dielectric anomalies, SHG, and single-crystal X-ray diffraction analysis. The pyroelectric measurements reveal that compound 1 is a Rochelle salt type ferroelectric, which has a large spontaneous polarization of about 3 μC/cm(2).

Molecular ferroelectric pyridin-2-ylmethanaminium perchlorate with phase transition induced by disorder of perchlorate

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15] Molecular ferroelectrics, as one class of ferroelectric materials, compared with the traditional inorganic ferroelectric materials, have some advantages, such as easy design, nontoxicity, and exibility. [16][17][18][19][20] The study of ferroelectricity began in 1920 with the research on the special dielectric properties of Rochelle salt by Valasek,21 which was nearly 100 years ago. Thereaer, a lot of ferroelectrics have been discovered, such as BaTiO 3 (BTO), 21,22 KH 2 PO 4 (KDP), 23 and LiNbO 3 .…”

“…24 The molecular ferroelectric diisopropylammonium perchlorate with spontaneous polarization ($23 mC cm À2 ), which is close to BTO ($26 mC cm À2 ), has been reported. 25,26 In addition, there are many molecular ferroelectrics that have superior ferroelectric properties, such as diisopropylammonium bromide, 27,28 18 and pyridin-4-ylmethanaminium perchlorate. 35 Herein, we discovered a new molecular ferroelectric pyridin-2ylmethanaminium perchlorate ( Fig.…”

Fabrication of diisopropylammonium bromide aligned microcrystals with in-plane uniaxial polarization

“…Molecular ferroelectrics are generally grown in the bulk by hydrothermal crystallization, efficiently producing high-quality single crystals measuring many centimeters in size [34], which is useful for a number of key applications, such as nonlinear optics [36]. To play a role in organic electronics, however, it is necessary to fabricate high-quality crystals in thin film form or as readily integrated micro-and nanocrystals.…”

Molecular Ferroelectric Piperidine‐4‐ylmethanaminium Perchlorate with Superior Switchable Dielectric Properties

“…In addition, there are some molecular ferroelectrics with excellent switchable dielectric properties, such as (CHA) 2 CdCl 4 , hexamethylenetetramine ferrocene carboxylic acid, hexamethylene‐tetramine bisnopinic acid, dabco⋅p‐nitrophenol, and so on. Recently, a number of pyridyl‐based molecular ferroelectrics have been discovered, such as PyX (Py =pyridinium and X = ClO 4 , BF 4 , ReO 4 , IO 4 ), (4‐amino‐2‐bromopyridinium) (4‐amino‐2‐bromopyridine) tetrafluoroborate, pyridin‐4‐ylmethanaminium perchlorate, and so on. However, there are few reports of piperidyl‐based molecular ferroelectricity.…”