The Growth And Properties Study Of Molecular Ferroelectrics With 4-amino-2-bromopyridine Cation

Ferroelectric materials play a pivotal role in memory devices,laser,communications and piezoelectric sensors with the development of electronic information technology,which all benefit from its characteristic in optics,electricity,magnetism,heat,dynamics.Nevertheless,the current ferroelectric materials have more or less defects,which restricts their further industrialization.As the best performance and most widely used ceramic ferroelectric material,Pb(Zr1-xTix)O3(PZT)has a high sintering temperature up to 600-900?,accompanied by the volatilization of toxic substances which cause great harm to the surrounding environment.In addition,the ceramic ferroelectric materials generally have lots of shortcoming including high density,high energy consumption,high rigidity,high coercive field.Therefore,it is imperative to improve the performance of ferroelectric materials,by exploring new varieties to make up for the defects of traditional ferroelectric materials.In recent years,comparing to inorganic ferrroelectrics,the molecular ferroelectrics have considerable development,which are cheap and non-polluting.The spontaneous polarization of diisopropylammonium bromide is more than 20 ?C/cm2,making it talent showing itself?In this paper,the properties and characteristics of this series of ferroelectric materials are presented by the preparation and characterization of the(4-Amino-2-bromopyridinium)Tetrafluoroborate.i.The properties and characteristics of(4-Amino-2-bromopyridinium)Tetrafluoroborate.Second-harmonic generation 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 2.67 times of that of KDP,and(4-Amino-2-bromopyridinium)Tetrafluoroborate(2),possessing more incredible large second-order nonlinear optical coefficient as high as 10.67 times that of KDP.The compound 1 undergoes two couple of reversible phase transition behaviors at around T1=244.1 K and T2 = 154.6 K,caused by the dramatic change of the dynamical state of the protonated cations and the order-disorder of anions,which was disclosed by DSC,heat capacity,dielectric anomalies,SHG,and single crystal XRD analysis.ii.The properties and characteristics of(4-Amino-2-bromopyridinium)hydriodic acid(3).The compound 3 was obtained by slow evaporation of a clear ethanol solution containing equal molar ratio of 4-amino-2-bromopyridine and hydriodic acid.The compound 3 undergoes one couple of reversible phase transition behaviors at around T = 190 K,which was disclosed by DSC and dielectric anomalies.By means of the comparative analysis between compounds 1 and 3,we have an opportunity to obtain better ferroelectric materials whose phase-transition temperature is higher and spontaneous polarization is greater.