Phase Transitions Of Hybrid Perovskite Based On DABCO And Its Derivatives

As a kind of electronic functional material,dynamic response materials have many physical properties that will change with external conditions,such as temperature-responsive dielectric phase transition and nonlinear optical properties,electric field-responsive ferroelectric phase transition,etc..Among them,the dielectric responsive perovskite-type materials have potential application value in the electronics industry and the intelligent transmission and control industry.Therefore,the design of novel dielectric responsive perovskite materials is of great value.Here,a series of organic-inorganic hybrid perovskite crystalline compounds have been successfully synthesized,and their single crystal structure,dielectric transformation properties and mechanism have been characterized in detail.The experimental research system of this thesis is mainly divided into the following three parts:the first part is the compound synthesized with 1,4-diazabicyclo[2.2.2]octane cation as the main body,which are H₂dabco(NH₄)(BF₄)₃(compound 1),H₂dabco Rb(BF₄)₃(compound 2),deuterated compound 1(compound 3).In the second part,N-methyl-1,4-diazabicyclo(2.2.2)octane cation is the main synthetic compound,which are[Me-Hdabco]Na(BF₄)₃(compound 4),one-dimensional compound[Me-Hdabco]K(BF₄)₃(Compound 5),three-dimensional compound[Me-Hdabco]K(BF₄)₃(Compound 6),[Me-Hdabco]Rb(BF₄)₃(compound 7).In the third part,the compounds synthesized with1-Fluoro-4-Methyl-1,4-diazabicyclo(2.2.2)octane cation as the main body are[1-F-4-Medabco]Na(BF₄)₃(Compound 8),[1-F-4-Medabco]K(BF₄)₃(Compound 9).As mentioned above,the structure,physical and chemical properties of the nine compounds were synthesized and analyzed in detail,and they have been measured by dielectric,DSC,single crystal structure,powder diffraction and other methods.The results show that all compounds have the dielectric phase transition.4,5,7,8,and 9 also have two pairs of continuous phase transition behaviors.Compound 9 crystallizes in the polar space group,showing a reversible SHG response.These nine compounds have potential application value in the field of molecular dielectric and optical materials.