The Synthesis And Properties Of Phase Transition Compounds Based On Aliphatic Cyclic Amines

Ferroelectric materials,an important topic in materials science,have been found to be widely used in non-volatile memories,surface acoustic wave devices,pyroelectric infrared detectors,energy harvesting,and nonlinear optical devices.Ferroelectric materials are usually thermodynamically structured phase transition materials that can undergo reversible paraelectric-ferroelectric phase transition in response to temperature,leading to the appearance and disappearance of spontaneous polarization.Currently,cyclic organic amines are considered strong contenders for the design of phase transition materials and high performance ferroelectric materials.In this thesis,14 organic-inorganic hybrid compounds based on cyclopropylamine,N-methylcyclohexylamine derivatives and cyclohexylamine as organic ligands were successfully synthesized and their dielectric,phase transition and ferroelectric properties were investigated.（1）[C₄H₃N]₂Cd Cl₄（1）,[C₄H₃N]₂Cd Br₄（2）and[C₃H₈N]₂Cu Cl₄（3）were obtained by reacting cyclopropylamine as an organic ligand with cadmium chloride,cadmium bromide and copper chloride,respectively.Among them,1 crystallizes in the tetragonal crystal system,P4₂/ncm space group,It was demonstrated by differential scanning calorimetry and dielectric properties tests that 1 underwent two consecutive reversible phase transitions near220 K/209 K and 287 K/264 K,respectively.2 also crystallizes in the tetragonal crystal system,P4₂/ncm space group and undergoes a reversible phase transition near 270 K/259 K.The dielectric property tests showed a pair of dielectric anomalies around 276 K/256 K for 2,further demonstrating that 2 is a reversible phase change compound.3 crystallizes in the monoclinic crystal system,C2/c space group and does not undergo phase transition behavior.（2）[C₇H₁₆N]₂Cu Br₄（4）,[C₇H₁₆N]₂Cd Br₄（5）,[C₇H₁₆N]₂Co Br₄（6）,[C₈H₁₈N]₂Cd Cl₄（7）,[C₈H₁₈N]₂Co Cl₄（8）,[C₈H₁₈N]₂Cd Br₄（9）,[C₈H₁₈N]₂Co Br₄（10）were obtained by reacting N-methylcyclohexylamine derivatives as organic ligands with transition metal halides,respectively.4-6 all crystallize in the trigonal crystal system,P^-1 space group.Among them,4 undergoes a reversible phase transition near 356 K/325 K,5 undergoes a reversible phase transition near 410 K/337 K,and the phase transition temperature of 6 reaches 414 K.The influence of the anion on the phase transition temperature of the compound was demonstrated by the selection of different transition metal elements in the anion.7crystallizes in the orthorhombic P2₁2₁2₁space group and undergoes a phase transition near a high temperature of 399 K.8 crystallizes in the monoclinic P2₁/n space group and undergoes a reversible phase transition behavior near 429 K/336 K.Both 9 and 10crystallize in the orthorhombic P2₁2₁2₁space group,where 9 undergoes two consecutive reversible phase transitions at 351 K/332 K and 424 K/356 K,and 10 undergoes two consecutive reversible phase transitions at 343 K/323 K and 455 K/369 K.9 compared to 7and 10 compared to 8,the halogen atoms change from Cl atoms to Br atoms,and the phase transition temperatures are successfully increased by 25 K and 26 K,respectively.It is further demonstrated that the anion has an effect on the phase transition temperature of the compound.（3）Two organic-inorganic hybrid molecular ferroelectrics[C₆H₁₃N]₂Cd Cl₄（11）,[C₆H₁₃N]₂Cd Br₄（12）and two organic-inorganic hybrid compounds[C₆H₁₄N]₂Cu Cl₄（13）,[C₆H₁₄N]Cu Br₃（14）were obtained by the reaction of cyclohexylamine as organic ligands with transition metal halides,respectively.11 and 12 are homologues both crystallized in the cubic crystal system,Cmc2₁ferroelectric space group.The ferroelectric phase transition temperatures of 368 K and 420 K for 11 and 12 were demonstrated by differential scanning calorimetry and dielectric properties tests.The saturation polarization value of 11 was measured as 0.083μC/cm²by hysteresis line measurement,and the saturation polarization value of 12 was theoretically calculated as 0.017μC/cm².The ferroelectric domains,phase hysteresis curves and butterfly curves obtained by piezoelectric microscopy tests further demonstrate the ferroelectric properties of 11 and 12.Compared with 11,12 successfully increased the ferroelectric phase transition temperature by 52 K through halogen substitution.13 crystallizes in the orthogonal crystal system,Pbca space group,and 14crystallizes in the orthogonal crystal system,P2₁2₁2₁space group,13 and 14 do not have ferroelectricity.In summary,this paper has successfully synthesized a series of promising phase change materials by using Cyclopropylamine,N-methylcyclohexylamine derivatives and cyclohexylamine as organic ligands,expanding the variety of phase change materials and providing the possibility of future ferroelectric material devices.