分子基多功能铁电单晶的设计、合成与调控

Molecule-based hybrid ferroelectric materials are a kind of supramolecular organic-inorganic salts, which is composed of multifunctional building blocks through intermolecular weak interactions. And the ferroelectric properties are closely related with its polar structure. Molecule-based ferroelectrics are a kind of very important new intelligent storage material with the characteristics of structure easy modification tailoring, easy to grow high-quality crystals, the synergy of functional primitives, especially lead-free and environmentally friendly, and easy to syncretize with organic or inorganic materials. Those characteristics mentioned above have attracted wide attention of researchers. The design, controllable preparation and versatility are composing of an important leading strategy for searching and seeking new ferroelectric materials based on the mechanism of the ferroelectric properties. It would be of important practical significance and academic value to carry out the controllable preparation of hybrid ferroelectrics, to investigate the underlying mechanism and to develop related theory. In this study, we plan to design several different series of order-disorder type ferroelectrics based on our research experience and theory models. This kind of ion-type compounds display a disordered feature which is the origin of ferroelectricity. Typical examples are deuterated pyridium or imidazolium salts whose ferroelectricity comes from the disorder-order transition of cations. Rotator-stator molecular ferroelectric is due to the disorder rotator dipole. To most of the ammonium salts with high Tc temperature, the mechanism goes to disorder cation. In this study, a series of ferroelectrics, such as host-guest skeleton structure, one dimention chain, molecular motors and superimposed layers model, will be designed and synthesized. And the structure and properties including ferroelectrcity, dielectricity, domain and piezoelectricity, domain, SHG response also will be investigated. Then the regulation of ferroelectric properties will be implemented through anion and cation replacement with the help of crystal engineering. In addition, we'll try to disclose the mechanism of ferroelectrics, and to develop ferroelectric physics suitable for molecule-based ferroelectrics to guide the further researches.

分子基铁电体为新型多功能存储材料，属于化学、材料、物理、电子等多学科前沿交叉研究。由有机和无机的结构功能基元通过超分子作用结晶构筑和实现性能调控。具有较鲜明的特点和良好的性能：易实现结构-性能的修饰调控、可引入多功能基元、光电磁多功能性、大尺寸晶体、无铅无重金属、常温制备简易节能。对科学研究和应用性来说展开分子铁电的多体系可控制备、偶极翻转机理、相关模型理论研究都具有重要的意义。分析分子铁电的机理进行有效设计、调控和实现多功能性是今后新型铁电材料研究的主要方向。本项研究拟合成三个体系模型的分子铁电材料，氢键链型、主客体型、分子马达型。并对变温结构、热焓、各向异性介电、压电、SHG 、微畴结构、铁电、光电磁场环境下的电性质等进行测试分析，为分子铁电研究建立系统的结构学和物理学研究方法。并结合朗道相变理论及第一性原理量化计算探讨铁电机理,促进分子基铁电研究的发展。

铁电体物理学与其它的学科领域不同,其跟晶体结构有着紧密联系。铁电体是一类重要的功能材料。有机无机杂化铁电体由于具有结构易剪裁、随用随丢、易于生长高质量的大晶体,尤其是环保和易于和有机材料整合等特点, 引起广泛关注。 从铁电性产生的基本原理出发设计及可控合成将是今后寻求新的铁电体的一个重要方向。开展杂化铁电体的可控设计制备,研究其铁电机理,发展相关理论具有非常重要实践意义和学术价值。本项目在过去研究氢键型和有序无序型铁电体的基础上,采用dabco、 冠醚、咪唑及其衍生物和类似的有机小分子以及大环醚和阴性骨架为构筑块，通过晶体工程控制分别获得并调控活性双稳态氢键型和有序无序型的超分子基介电铁电单晶和薄膜，并对其变温结构、介电、压电、SHG 、铁电等相应性质进行了系统深入的研究。 深入探讨了该类介电铁电材料的机理,促进了分子基介电铁电材料的物理学研究。发表SCI论文8篇，IF大于4的5篇，其中IF大于10的一篇。