Synthesis,Dielectric And Ferroelectric Properties Of Organic-Inorganic Hybrid Phase Change Compounds Based On Flexible Organic Ammonium

Structural phase transition materials whose physical properties（optical,electric and magnetic）can be control by external stimulated（temperature,pressure,electric and magnetic field）,have become the forefront of scientific research in recent years,due to their excellent dielectric,pyroelectric and ferroelectric properties that can be apply to switches,sensors and memory devices.In particular,organic-inorganic hybrid phase transition materials have attracted great attention due to their advantages of both organic and inorganic components as well as easy to adjust structure and properties.Numerous researches show that introducing the order-disorder transformation of organic components is an effective strategy for designing organic-inorganic hybrid phase transition materials.Therefore,flexible organic components which are easy to show disorder at high temperature are wonderful candidates,such as methylamine,dimethylamine,trimethylamine,cyclohexylamine,phenethylamine,phenylbutylamine,triethylenediamine and its derivatives.On the basis of the previous researches,seven organic-inorganic hybrid compounds based on trimethylamine,phenylethylamine,4-chlorophenylamine,cyclohexylamine and 4-methylcyclohexylamine have been synthesized and studied their single crystal structures,thermal,optical,dielectric and ferroelectric properties.This thesis consists of five chapters.In chapter 1,a briefly introduction of structural phase transition materials and ferroelectric materials,including their definition,classification and research progress.In Chapter 2,an organic-inorganic hybrid phase transition compound[（CH₃）₃NH]₄[Fe（SCN）₆]Cl（1）based on trimethylamine was synthesized,and studied its order-disorder phase transition mechanism and the Debye type dielectric relaxation behavior base on its single crystal structures and dielectric properties.In chapter 3,two organic-inorganic hybrid phase transition compounds based on phenylethylamine and4-chlorophenylamine were synthesized,and proved that（C₆H₅CH₂CH₂NH₃）₂[Hg I₄]（2）is a near room temperature molecular-based ferroelectric compound.Its ferroelectric transition mechanism can ascribe to order-disorder change of phenethylammonium cation.（4-Cl-C₆H₄CH₂CH₂NH₃）₂[Cd I₄]（3）is a potential ferroelectric compound with a high transition temperature.In chapter 4,four organic-inorganic hybrid compounds based on cyclohexylamine and 4-methylcyclohexylamine were synthesized,including a potential molecular-based ferroelectric compound C₆H₁₁NH₃I·C₆H₁₁NH₂（4）,a potential high temperature molecular-based ferroelectric(C₇H₁₄NH₃)₂[Cd Cl₄]（5）,and two molecular-based magnetic compounds(C₆H₁₁NH₃)₄[Mn₃Cl₁₀（H₂O）]（6）and(C₆H₁₁NH₃)[Mn Br₃]（7）.In chapter 5,a brief summary and prospect of the thesis.