分子铁电体具有质轻、环保、结构可控、自发强度和相变温度可调等优点，对新型铁电材料发展意义重大。具有无序AO4n-阴离子 (A = S, P，Cl, Br, As等, n= 1, 2, 或 3)化合物繁多，随外界条件变化可能从内部单个、多个氧原子无序到与主客体分子协同无序，为无序-有序型分子铁电体研究提供了新的思路。. 对晶体学数据库研究梳理，构筑系列由AO4n-阴离子无序-有序化诱导结构相变的转子-定子型、钙钛矿型和插层结构的化合物；利用变温X-射线单晶衍射仪、固体NMR等确定不同温度的精细结构，研究其对称性破缺，结构相变和自发极化机理；借助SHG效应判断铁电相空间群的正确性；通过介电、DSC测试仪等表征其随温度变化的介电和热异常行为，确定居里相变温度；揭示AO4n-阴离子无序-有序化运动对结构相变、自发极化和铁电性能的影响，为寻找高自发极化率、低介电常数、高相变温度铁电体提供新途径。

Research on molecular ferroelectrics is of great significance in the development of ferroelectric materials since they are promising with light, environmental friendly, tunable structures, controllable spontaneous polarization and Curie temperature etc. Compounds containing AO4n-(A = S, P, Cl, Br, As etc, n= 1, 2 or 3) anions may exist a lot kinds of disordered states which varied from one or more disordered oxygen atoms to the whole double or multiple disordered AO4n- anions, even more they can coordinate with other disorder negative ions, positive ions and molecules, which provided a plentiful of resource for the research of molecular ferroelectrics.. In this project, through CCDC data carding, we aim on designing and synthesizing serials of AO4n- anions compounds with rotor-stater type, perovskite type, and inter-layered structures, which can induce the structural phase-transition via the disordered-ordered AO4n- anions. We obtain their structures at different temperatures by X-ray single crystal diffraction, Solid state NMR and PXRD, then analysis the symmetry breaking, reversible structural phase-transition and mechanism of spontaneous polarization, and then judge the space group of ferroelectric state through SHG (second harmonic generation) effect test. Furthermore, we determine their heat and dielectric anomaly by temperatures evolution of DSC (differential scanning calorimetry) and dielectric measurement, and prove the phase-transition temperature, then investigate the impact on structural phase-transition, spontaneous polarization and ferroelctricity from the disorder-order motion of AO4n- anions in host-gust molecules. We hope our study provide some new ideas for the seek of new-type ferroelectrics with high spontaneous polarization value, low dielectric constant and high phase transition temperature.