Synthesis And Ferroelectric-dielectric Properties Study Of Nopinic Acid Type And Metal Thiocyanates Type Compounds

Since ferroelectric materials generally have excellent dielectric,piezoelectric,pyroelectric and optical properties,they have very broad application prospects in multifunctional materials.Research on finding compounds with reversible phase transitions has been very popular in recent years.In this paper,we synthesized a series of nopinic acid compounds,synthesized a series of rare earth thiocyanate compounds and crown ether inclusions containing thiocyanate ions compounds,and studied their crystal structure and phase transition behavior.The main contents of this paper are as follows:1.Briefly introduce the related concepts and definitions of ferroelectric-dielectric materials,and combine the research status of phase change materials at our country and abroad.The system describes the nopinic acid compounds,rare earth thiocyanate compounds and crown ethers containing thiocyanate ions compounds.The research status of inclusion complexes in ferroelectric-dielectrics.It also fully explains the basis of the topic and the research progress obtained.2.Using nopinic acid as raw material,directional assembly of nopinic acid molecules and amines gave three compounds,namely:2C₁₀H₁₆O₃?C₆H₁₂N₄?1?,2C₁₀H₁₆O₃?C₆H₁₂N₂.H₂O?2?,C₁₀H₁₅O₃?C₁₂H₁₄N?3?,Dielectric constant tests show that both Compound 1 and Compound 3 have reversible phase transitions at low temperatures,with phase transition temperatures of 240 K and200 K,respectively.The ferroelectric test showed that both Compound 1 and Compound 3 had good hysteresis loops.Second-order nonlinear generation?SHG?studies show that compounds 1-3have strong second-order nonlinear optical signals.3.Using benzyl triphenylphosphine and tetrabutylamine as cations,four compounds were synthesizedbyrareearthnitrateandammoniumthiocyanate,respectively:3C₂₅H₂₂P?Gd?NO₃?₂?SCN?₄?4?3C₂₅H₂₂P?Ho?NO₃?₂?SCN?₄?5?,3C₂₅H₂₂P?Er?NO₃?₂?SCN?₄?6?,3C₁₆H₃₆N?Er?NO₃?₂?SCN?₄?7?.Experimental studies have shown that the molecules of compounds4-6 have a certain degree of disorder,but not enough to cause structural phase transition.Compound 7 has a reversible phase transition under low temperature conditions,and the phase transition temperature is about 140 K.The analysis of the temperature-varying single crystal structure test reveals its phase transition mechanism.The emission and excitation spectra of Compound 7 were tested by fluorescence spectroscopy.4.Based on the inclusion of crown ether and amine,the thiocyanate ion and transition metal were introduced for coordination,and four crown ether inclusion complexes containing thiocyanate ion were successfully synthesized.2?18-crown-6?KC₅H₁₂N?Co?SCN?₄?8?,2?18-crown-6??2C₅H₁₂N?Co?SCN?₄?9?,2?18-crown-6??2C₅H₁₂N.Mn?SCN?₄?10?,2?18-crown-6??2C₆H₁₄N?Co?SCN?₄?11?.Dielectric constant tests show that compound 10 has a reversible phase transition around 100 K at low temperature,and there is a reversible phase transition near 393 K.Compound 11 has a reversible phase transition near 413 K.