有机铵卤化铟铁电材料的合成、结构及性质研究

Organic-inorganic hybrid ferroelectric material is one of the current research focuses and development trends of ferroelectric material. In this project, the strategy of regulating the hydrogen bond strength between the organic and inorganic ions will be adopt. The organic amines, which easy to occur disorder-order transition, will react with indium halides at different conditions to prepare organic ammonium indium halides with different compositions and structures. The hydrogen bonds with different intensities will be constructed and regulated, which will promote the disorder-order transition of the organic ammonium cations and thereby induce the structure phase transition of the compound. The compounds with ferroelectric phase transition will be filtered out by the temperature dependence of the dielectric permittivity, differential scanning calorimetry measurement and variable temperature single crystal structure determination. Their crystal structure, structural phase transition, dielectric and ferroelectric properties of single crystals will be detailed studied. The Landau theory of phase transition and Curie's principle of symmetry can be used to analyse the structural phase transition. Furthermore, the source and mechanism of the ferroelectric property will be expounded by means of symmetry breaking theory and structural variations. On this basis, the relations and laws between the structure, intensity of the hydrogen bonds and phase transiton, ferroelectric performance will be explored and discussed.

有机-无机杂化铁电材料是当前铁电材料的研究热点和发展趋势之一。本项目采用调控有机、无机离子间氢键作用强度的策略，选择易于发生无序-有序转变的有机胺与卤化铟在不同反应条件下制备出组成和结构多样的有机铵卤化铟系列化合物，构建和调控不同强度的氢键以利于有机铵离子发生无序-有序相变，从而诱导化合物发生结构相变。通过变温介电常数测试、差示扫描量热分析和变温单晶结构筛选出发生铁电相变的目标化合物，系统研究化合物的晶体结构、结构相变、单晶体的介电和铁电性质。应用朗道相变理论和居里对称性原理分析化合物的结构相变，并结合对称性破缺理论和结构变化信息阐明铁电性的来源和产生机理。深入探讨化合物的结构、氢键强度与结构相变和性能之间的关系和规律性。

按照项目计划开展相关研究工作，取得以下重要研究成果。Ⅰ、选取环状胺（四氢吡咯、4-甲基咪唑、苯乙胺）为模板与卤化铟反应制备了三种有机-无机杂化相变材料。详细研究了三种化合物的晶体结构、相变机理、介电以及铁电性质。[InBr4]−阴离子有序-无序转变、4-甲基咪唑阳离子的有序-无序转变和[InBr4]−阴离子无序程度的变化、苯乙胺阳离子的有序-无序转变分别引起这些化合物发生结构相变。Ⅱ、选取小分子链状胺（甲胺、乙胺、正丙胺、四丙基胺）为模板与卤化铟反应制备了四种有机-无机杂化相变材料。详细研究了它们的结构相变以及介电性质。甲胺阳离子与[InCl6]3−阴离子、乙胺阳离子、正丙胺阳离子、[InCl4]−阴离子的有序-无序转变分别导致化合物发生结构相变。Ⅲ、以有机二胺（1, 5-戊二胺、1, 3-丙二胺、2, 2-二甲基-1, 3-丙二胺）为模板与卤化铟反应制备了三种有机-无机杂化相变材料。研究了它们的晶体结构、相变机理、介电以及铁电性质。1, 5-戊二胺阳离子和2, 2-二甲基-1, 3-丙二胺阳离子的有序-无序转变是驱动相变的主要因素，化合物是介电可调材料。[(NH3)(CH2)3(NH3)]2[InBr6]Br·H2O的相变可归因于1, 3-丙二胺阳离子的相对位移和结构扭曲，该化合物具有良好的介电性与铁电性。应用朗道相变理论阐明了铁电性的产生机理，深入探讨了化合物结构与性能之间的关系和规律性。