Synthesis,Structure And Ferro-dielectric Materials Of Low-dimensional Ionic Reversible Phase Transition Compounds

Ferroelectric phase change materials have huge potential applications in the field of multifunctional materials.In this thesis,a total of eight compounds have been synthesized.Through various characterization methods,the structure,optical properties and iron dielectric properties of these compounds have been studied.The main contents of this paper are as follows:(1)In this paper,by adjusting the different proportions of ligands such as thiocyanate and nitrate to form different rare earth anion groups with rare earth ions,using flexible tetrabutylammonium cation to balance the charge,and synthesize[Tm(SCN)₆][(TBA)₃](1)and[Ce(NO₃)₄(SCN)₂][(TBA)₃](2)[TBA⁺=tetrabutyl-ammonium cation]two rare earth compounds.X-ray single crystal diffraction analysis shows that compound 1 belongs to in the center symmetry space group P-1 in the triclinic system at room temperature,while compound 2 belongs to the non-center space group Cc in the monoclinic system,indicating that by reducing the symmetry of the rare earth anion group,the centrally symmetric compound 1 is adjusted to the non-center space group compound 2.(2)Three compounds were successfully synthesized by the solution method:[N(CH₂CH₃)₃(CH₂Cl)][Cl O₄](3),[N(CH₂CH₃)₃(CH₂Cl)][PF₄](4)and[N(CH₂CH₃)₃(CH₂Cl)][Fe Cl₄](5).3 and 4 have plastic phase transition behavior,and 5 has excellent nonlinear optical behavior.Through dielectric measurement,differential scanning calorimetry(DSC)and X-ray single crystal diffraction and other characterization methods,it can be known that compounds 3 and 4 have undergone two phase transitions above room temperature,and the second phase transition is plastic phase transition.Compounds 3 and 4 are both crystallized in a trigonal crystal system with chiral space group P3₂21.Both have a positive Cotton effect,indicating that 3 and 4 are monochiral compounds.(3)Three crown ether compounds were synthesized by solution method:[NH₃CH₂CH₂Cl(18-crown-6)][Cl O₄](6),[NH₃CH₂CHF₂(18-crown-6)][Cl O₄](7)and[C₆H₁₁NO(18-crown-6)][Cl O₄](8).Through dielectric testing,differential scanning calorimetry,X-ray single crystal diffraction and other characterization methods,indicating that compounds 6,7 and 8 have all undergone reversible phase transition.Compound 6 crystallizes in the chiral space point group P2₁2₁2₁ at room temperature and has good nonlinear optical activity.