Synthesis And Properties Of Molecular Ferroelectric And Dielectric Materials Based On Anion And Cation Regulation

In the past 20 years,because of their excellent electrical and optical properties,compared with ceramic materials,molecular based ferroelectric materials have the advantages of light weight,environmental friendly?without lead,etc.?,good flexibility,easy forming and synthesis,which have attracted a lot of interest of scientific researchers and attracted a lot of attention of scientific researchers.According to this characteristic,two crown ether-K⁺,three crown ether-H₃O⁺,five crown ether organic amine host guest complexes and three discrete tetrahedral ion building compounds were successfully synthesized.The structure and properties of the synthesized compounds were studied by means of single crystal diffraction,variable temperature dielectric constant test,differential scanning calorimetry,secondary nonlinear optics and hysteresis loop.The main contents of this paper are as follows:1.Using 18-C-6 as a fixed raw material,by designing how to synthesize compounds with high-temperature reversible phase transitions and ferroelectric properties,5 compounds were successfully synthesized,namely compound[H₃O?18-C-6?]⁺[CdCl₄]^-?1?,compound[H₃O?18-C-6?]⁺[FeBr₄]^-?2?,compound[K?18-C-6?]⁺[PF₆]^-?3?,compound[K?18-C-6?]⁺[CrO₃F]^-?4?,compound[H₃O?18-C-6?]⁺[FeCl₄]^-?5?.Compound 2 has a low-temperature phase transition with a phase transition temperature of 240 K.Compound 3-4 has a temperature reversible structural phase transition with a maximum phase transition temperature of up to 340K and 374 K.Compound 5 has a high-temperature ferroelectric phase transition with a polarization value of approximately 2.18 uC/cm^-2;2.According to the structure of"lock and key"formed easily by crown ether,primary amine and secondary amine,five compounds were successfully synthesized by using 18-C-6 as"lock"and related organic amines,among which compound 6-7uses inorganic acid to balance the charge and has a low-temperature reversible phase transition temperature of 250 K and 220 K,respectively.Compound 8 uses the organic acid trifluoromethylsulfonic acid to balance the charge,which has a high temperature and can result in a phase transition temperature of 340 K;compound 9and compound 10 use the chiral amine D-cysteine as the"key",different acids can get different products,both of which have positive cotton effect and strong SHG effect.3.According to the rotatability of tetrahedron,it is easy to change from order to disorder.At the same time,tetrahedron is transformed into tetrahedron with lower symmetry and easier to crystallize in non-central polar point group.Through this idea,three similar compounds have been synthesized in this paper,namely compound 11,tetramethylchlorochromate,which has a low-temperature reversible phase transition temperature of 240 K;compound 12,chloromethyltriethylammonium chloride chromate,which crystallizes in non-central group,has a high-temperature phase transition temperature of 330 K;compound 13,1,3-bis?4-pyridyl?propane perchlorate has a low-temperature phase transition temperature of 250 K,accompanied by the on and off properties of SHG.