New Molecular Ferroelectrics Accompanied by Ultrahigh Second-Harmonic Generation.
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).
Collaborative Innovation Center of Advanced Microstructures, Lab of Solid State Microstructures, School of Physics, Nanjing University , Nanjing 210093, People's Republic of China.
Chuang
C
Liu
Collaborative Innovation Center of Advanced Microstructures, Lab of Solid State Microstructures, School of Physics, Nanjing University , Nanjing 210093, People's Republic of China.
Kaige
K
Gao
Collaborative Innovation Center of Advanced Microstructures, Lab of Solid State Microstructures, School of Physics, Nanjing University , Nanjing 210093, People's Republic of China.
Zepeng
Z
Cui
Collaborative Innovation Center of Advanced Microstructures, Lab of Solid State Microstructures, School of Physics, Nanjing University , Nanjing 210093, People's Republic of China.
Linsong
L
Gao
Ordered Matter Science Research Center, College of Chemistry and Chemical Engineering, Southeast University , Nanjing 211189, People's Republic of China.
Da-Wei
DW
Fu
Collaborative Innovation Center of Advanced Microstructures, Lab of Solid State Microstructures, School of Physics, Nanjing University , Nanjing 210093, People's Republic of China.
Hong-Ling
HL
Cai
Collaborative Innovation Center of Advanced Microstructures, Lab of Solid State Microstructures, School of Physics, Nanjing University , Nanjing 210093, People's Republic of China.
X S
XS
Wu