Synthesis,Magnetic And Dielectric Properties Of The Compounds With Perovskite-Like Structure

Recently,perovskite-like ferroelectric and ferromagnetic materials have attracted extensive attention because of their important applications in communication,information storage,infrared sensing and piezoelectric sensing.Some perovskite-like compounds have excellent ferroelectric,ferromagnetic or phase transition properties.Under the excitation of external conditions,the dielectric heterosample and thermal anomaly may occur in the vicinity of the phase change point.When looking for phase change materials with ferroelectric or ferromagnetic properties,the complexes that formed by transition metals tend to have excellent ferromagnetism,and ammonium salts containing nitrogen have a unique polar structure and including hydrogen bonds and the possibility of disorder,which provide theoretical guidance for the search for ferroelectric and ferromagnetic phase transition compounds.Therefore,single crystals of complexes are usually synthesized by inorganic transition metal halide and organic ammonium salts that containing nitrogen,or designed metal-organic framework that constructed by transition metal and cyano,thiocyanate,azide,dicyanoamine.The organic ammonium salt that containing nitrogen is the guest molecule and further coordinated with the organic framework to obtain the single crystal of the compounds.Generally,we determine the occurrence of phase transition by measuring the dielectric anomaly associated with the reversible peak of DSC.According to Curie-Weiss law,the change of dielectric constant with temperature obeys ?=?e+C/?T-T₀?,and the dielectric constant of the sample near the phase transition point will have obvious mutation.In order to find perovskite-like compounds with magnetic and dielectric phase transition,a series of organic-inorganic hybrid ligands were synthesized,their structures,magnetic properties and dielectric properties were studied.This thesis is divided into six parts:the first part summarizes the basic theory of single crystal,magnetic and dielectric phase transition and the development of related research at home and abroad,the second part briefly introduces the main experimental instruments and reagents;In the third part,we introduce the magnetic properties of the compounds that designed by the N₃^-?CN^-?N?CN?₂^-and SCN^-bridging ligands.In the fourth part,?2-bromoethyl?trimethyl ammonium bromide??2-BrEt?NMe3Br?was used as raw material to react with metal halide to construct organic-inorganic perovskite-like structural compounds and to study their magnetic and dielectric properties.Dielectric and thermodynamic properties show that the five compounds[?2-BrEt?NMe₃]₈[CoCl₄]₄,[?2-BrEt?NMe₃]₂CuCl₄,[?2-BrEt?NMe₃]₂CdCl₄,[?2-BrEt?NMe₃]PbBr₃,[?2-BrEt?NMe₃]₈[ZnCl₄]₄ have phase transition behaviors.In the fifth part,under the reaction of tetraethylammoniumbromide?Et₄NBr?and metal halide salt,compound[Et₄N]₂[PbBr₃]₂ was synthesized.In addition,under the reaction of butyltrimethylammoniumchloride?BuNMe₃Cl?and metal halide salt,compound[BuNMe₃]₂CdBr₄,[BuNMe₃]₃Sb₂Cl₉ were synthesized.The structure and dielectric properties of the three compounds were studied.The dielectric and thermodynamic properties show that[Et₄N]₂[PbBr₃]₂ and[BuNMe₃]₂CdBr₄ have phase transition behaviors.The sixth part summarized and analysised the full text,and looks forward to the follow-up works.