| Ferroelectric materials were payed close attention for its important role in information storage,infrared sensing,communication,piezoelectric sensing and other aspects.Most ferroelectric materials undergo phase transitions in certain temperature ranges and perform significant difference of thermodynamic and dielectric anomalies near the phase transition In order to find potential ferroelectric materials,we have synthesized one nopinic acid,ten crown ether clathrates and its metal derivatives and five organic-inorganic hybrid perovskite compounds,preliminarily investigated in their crystal structures and phase transition behaviors by single-crystal X-ray diffraction,elemental analysis,infrared spectra,powder X-ray diffraction analysis,dielectric constant-temperature curve test and differential scanning calorimetry?DSC?analysis.In chapter 1,a brief introduction of the properties and the reseach progress of the molecule ferroelectric materials.Expound the research status of nopinic acid and its derivatives,the crown clathrates and its metal derivatives,organic-inorganic hybrid perovskite compounds.The research significance and main results of this thesis are also summarized.In chapter 2,the nopinic acid was synthesized by oxidation reaction of ?-pinene and its purity can be reached to 95% after Infrared spectra,Elemental analysis,NMR characterization,X-ray Single-crystal and powder diffraction?XRD?analysis.By the Measurement of dielectric constant,Differential Scanning Calorimetry?DSC?,Ferroelectric hysteresis loop and Thermal gravimetric analysis,we can conclude that the nopinic acid is a molecule ferroelectric material with the phase transition temperature of 157 K and large spontaneous polarization?Ps?of ca.16.94 ?C cm-2.In chapter 3,seven crown clathrates C12H24O6·C4H13N2+·ClO4–?2??C12H24O6·C4H13N2+·BF4–?3?? C12H24O6·C5H15N2+·ClO4–?4?? C12H24O6·C5H15N2+·BF4–?5??C12H24O6·C8H14N+·BF4–?6?? C12H24O6·C6H10N2+·ClO4–?7?? C12H24O6·C5H14N2+·BF4–?8?were obtained by using 18-crown-6 as host molecule and amine as guest molecule,They all appear dielectric strange and reversible temperature structural changes of 2 ? 4 ? 6 ? 7 by DSC measurement with the phase transition temperature of 379 K ? 394 K ? 393 K ? 382 Krespectively.We can make the conclusion that the four crown clathrates occur structural phase transition.with further variable-temperature XRD analysis.In chapter 4,on the basis of crown clathrates,three metal crown clathrates.[C4H4N-?18-crown-6?]+[FeCl4]-[H2O]?9??[C4H12N2-?18-crown-6?]+[ZnCl4]-?10??[C4H12N2-?18-crown-6?]+[CoCl4]-?11?were successfully synthesized by introduced FeCl3,ZnCl2,CoCl2.Interestingly,we discover that the coumpoud 9 is a cystal material with both high temperature and low temperature reversible phase transition by Dielectric,DSC,variable temperature XRD,variable temperature Raman spectroscopic and X-ray diffraction structural mesurement,which is of great value and significance to explore more ferroelectric materials.In chapter 5,five organic-inorganic hybrid perovskite materials?C4H9NH3?PbI3?12??(C6H15N2)PbI3?13??(C7H11N2)2PbI3?14??(C6H17N2)PbI3?15???BiI3??C2H8NO?3?H2O??16?were got by using PbI2/BiI3 with various synthetic organic amine molecules.Single-crystal structure analysis showed that the compound formed a two-dimensional network structure by intermolecular forces.To investigate their dielectric properties,powder diffraction?XRD?,infrared spectroscopy?IR?,the compound 16 performed a high temperature dielectric and DSC reversible abnormal changes with the phase transition temperature of 363 K for hydrogen bonding disorder between ethanolamine molecules. |
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