The Structure And Dielectric Properties Of Compounds Containing Organic Phosphate And Spiro-ammonium

Phase transition materials,especially ferroelectric materials act as an important kind of promising functional materials,which have attracted more and more attention because of its applications in high-technology fields such as data storage,communication,infrared sensing and piezoelectric sensing.Remarkably,phase transitions of crystals generally lead to the changes in crystal structures and symmetries.Not only that,the physical properties including dielectric properties,thermal properties or other properties will also display prominent anomalies in the vicinity of the phase transition temperature.Organic-inorganic hybrid materials possessing the advantages of both organic and inorganic compounds can simultaneously show structure controllability and stable property,which have an excellent performance in actual applications.In order to search new phase transition materials,we have designed and synthesized a series of organic-inorganic hybrid compounds based on the trimethylphosphonium derivative and spiro-ammonium,and studied their possibility of phase transition by means of structure analysis,permittivity measurement and differential scanning calorimetry(DSC).This thesis consists of 12 crystalline structures:[(CH3)3PCH2CH2P(CH3)3][ZnBr4](1)?[(CH3)3PCH2CH2P(CH3)3][MnN3C3S3OH]·2H2O(2)?[(CH2CH3)3PCH2CH2P(CH2CH3)3][CuBr4](3)?[(CH2CH3)3PCH2CH2P-(CH2CH3)3]2[Cd3C8N12Br6](4)?[(CH3)3P(CH2)4P(CH3)3][CdBr4](5)?[(CH3)3P-(CH2)4P(CH3)3][Cd(SCN)3]2(6)?[(CH3)3PCH2CH2CH2NH3][PbBr4](7)?[(CH3)3P-CH2CH2CH2NH3][Cdl4](8)?[C!2H2406][(CH3)3PCH2CH2CH2NH3][CdBr4](9)?[C12H2406][(CH3)3PCH2CH2CH2NH3][ZnBr4](10)?[(CH2)4N(CH2)4]2[ZnBr4](11)?[(CH2)4N(CH2)4]2[CdBr4](12).The infrared spectroscopy(IR),power diffraction(PXRD),crystal structure and the dielectric properties of twelve compounds have been charactered and analyzed respectively.Experimental results show that 2,3,10 display the step-like temperature-dependent dielectric anomaly in the low-temperature phase,the DSC curves also reveal the distinct exothermic and endothermic peaks near the phase transition point,which further verifies these three compounds undergo the reversible structure phase transitions.6,11,12 show the platform-like temperature-dependent permittivity anomaly and the DSC measurement also give the coincident results to demonstrate the reversible phase transitions.The origins of the phase transition on 6 are ascribed to the totally disordered of the phosphonium cations in high temperature and the deformation of the one-dimensional chain[Cd(SCN)3]n.The phase transition of 12 are triggered by the conformation changes of the the spiro-ammonium cations and the reorientation of the anions.Other compounds appear no reversible dielectric anomaly in the whole heating and cooling process,which means these compounds possibly not possess the phase transitions behavior.