Study On Crystal Dielectric Phase Transition Based On N-methylmorpholine Quaternary Ammonium Salt Derivatives

The demand for materials such as sensors and memories used in electronic devices has increased sharply,and there are higher requirements for the performance of these materials.The most important thing to support the digital economy and digital applications is the materials of the hardware equipment.Digital economy and digital applications involve materials such as storage,communication,display,and sensing.After more than half a century of development,researchers have explored many excellent properties of perovskite.Organic-inorganic hybrid perovskite,as the most studied type of material,exhibits almost all known physical properties,which will make it have more and more important application potentials in the future.Although the most mature application of organic-inorganic hybrid perovskite is solar cell,which has proven an efficiency of 25.5%so far,other energy and electronic applications based on organic-inorganic hybrid perovskite are also catching up.Due to the structural diversity and tunability of organic-inorganic hybrid perovskite,it can exhibit a variety of excellent properties,such as orderl-disorder phase transition,piezoelectricity,ferroelectricity,nonlinear optical properties,and thermally induced discoloration,photoluminescence.Therefore,organic-inorganic hybrid perovskite can become a very promising multifunctional material to meet the huge application needs of the digital age.The main content of this thesis is described in the following two parts.In the first part,five types of one-dimensional hybrid perovskites are synthesized by using N-methylmorpholine derivative quaternary ammonium salt cations to occupy the A position of the organic-inorganic hybrid perovskite,namely(CM)PbBr₃?(BM)PbBr₃?(FE)PbBr₃?(CE)PbBr₃?(BE)PbBr₃.In the second part,five kinds of zero-dimensional organic-inorganic hybrid crystals were synthesizedwithN-methyl-N-chloromethylmorpholineandN-methyl-N-bromoethylmorpholine as organic components,respectively(CM)₂Zn Br₄?(BE)₂Zn Br₄?(BE)₂Cd Br₄?(NEM)Cd Br₄?(NEM)Zn Br₄.The dielectric properties,optical properties,and thermal properties are tested by dielectric measurement,DSC,single crystal X-ray diffraction,ultraviolet-visible spectroscopy,SHG and other characterization methods.After characterization,the first five lead-based perovskite crystals are one-dimensional and multifunctional.According to the results obtained by dielectric and DSC,it is shown that except for(BE)PbBr3 without phase change in the test temperature range,the other four lead tribromide perovskites all have significant phase changes above room temperature.At the same time,under the irradiation of a handheld UV lamp,these five crystals all showed a red light.Characterized by fluorescence spectroscopy,it is proved that they do have the photoluminescence characteristics of red light emission.The other five zero-dimensional hybrid crystals of zinc and cadmium did not show outstanding performance.