Preparation And Research Of Anionic Disordered And Organic-inorganic Hybrid Perovskite Iron Dielectric Materials

Duo to molecular ferroelectric-dielectric materials have important properties such as dielectric,piezoelectric,ferroelectric,pyroelectric,ferro-elastic,nonlinear optics,optoelectronics,etc.,and have been the focus of research in the field of material chemistry.How to reasonably and effectively design and synthesize high-spontaneous polarization,high remanent polarization,and multi-functional molecular ferroelectric-dielectric materials have gradually become an important part of research.In many molecular ferroelectric-dielectric materials research systems,the anion similar to the spherical structure is easy to produce the order-disorder transition,organic-inorganic hybrid perovskite crystal structure has a higher Lorentz factor,more likely to produce spontaneous polarization.Based on the above two points,the main research direction of this paper is anionic disordered type and organic-inorganic hybrid perovskite type ferroelectric-dielectric multifunctional materials.The main research contents are as follows:?1?Firstly,the concept of symmetry in crystallography is introduced,and the relation between symmetry breaking and phase transition is pointed out.Then the microscopic mechanism and macroscopic phenomena of electric polarization are explained,and the characteristics of ferroelectrics are explained reasonably combining with phase transition.Finally,according to the previous work,the significance of this paper and the main research content.?2?A molecular ferroelectric material was synthesized,[?CH₂OH?₂][Cu(C₁₂H₈N₂)₂·SO₄]?1?.1undergoes the symmetry breaking from C2/c to Cc around 245 K,which triggered by disorder-order transition of sulphate anions and hydrogen bonds.That is a reversible paraelectric-ferroelectric phase transition.The ferroelectric properties measurement shows a maximum spontaneous polarization P_s=3.27?C·cm^-2 with coercive field E_c=1.2 kV·cm^-1.?3?A molecular reversible phase transition material was synthesized,[K(C₁₂H₂₄O₆)]FeCl₄?2?,which exhibits reversible phase transition around 135 K.This special phase transition behaviours were further confirmed by the heat and dielectric anomalies in the vicinity of 135 K.The structural transition mechanism can be attributed to the ordering-disordering motion of the tetrachloroferrate anions.?4?A novel perovskite molecular ferroelectric material was synthesized,(C₄H₁₀NO₂)₂CdCl₄?3?,which shows curie temperature T_c=355 K and spontaneous polarization Ps=7.2 uC/cm².Especially,the further investigation shows that 3 is a direct-gap semiconductor with band gap?3.88eV?.X-ray single crystal diffractions measurement at 293 and 365 K reveals that the twist motions of?-aminobutyric acid triggered the para-ferroelectric phase transition.?5?A novel perovskite molecular reversible phase transition material was synthesized,(C₄H₁₀NO₂)₂CdCl₄?4?,which underwent a solid reversible phase transition at 390 K.The single crystal X-ray showed that the ordered-disordered motion of the guest molecules of 1,3-diamino-2-hydroxypropane and the torsional motion of the Cd-Cl-Cd anion skeleton together led to the reversible phase transition.The direct band gap with value 4.40 eV,it has potential application on semi conductive materials.