一维氢键型铁电体的可控合成,性能及相关理论的研究

There are very few other sciences like physics of ferroelectrics which is so closely related with the crystal structure.Ferroelectric is an important class of functional material. In recent years, organic ferroelectrics, which would be with easily tailed structure, environmentally friendly, easily disposable, easy to grow high quality crystals, especially easily integrated with organic materials, have begun to attract wide concern of scientists. For the search of new ferroelectrics in the future, it is an important direction to design and controllably synthesize organic ones according to the basic principles of ferroelectrics. It would be of important practical significance and academic value to carry out the controllable preparation of organic ferroelectrics, to investigate the underlying mechanism and to develop related theory. This project is proposed on the basis of our experience of study on organic H- bond ferroelectrics in the past. .We plan to use 1,4 - diazabicyclo [2.2.2] octane (dabco) and pyrazine analogues as building blocks. By partial protonation of them, we may controllably synthesize one-dimensional H-bonded chains structures; By variation of substituent, we may control crystal packing in ferroelectric space groups; we may achieve ferroelectricity by utilization of bistable hydrogen bonds. Investigations in this project include structure and properties including ferroelectrcity, dielectricity and piezoelectricity, SHG response of organic crystalline materials. By combination of Landau theory of phase transitions and First principles quantum-chemical calculations, we’ll try to disclose the mechanism of ferroelectrics, and to develop ferroelectric physics suitable for molecular-based ferroelectrics.

很少有别的科学像铁电体物理学一样,跟晶体结构有着如此紧密的关系.铁电体是一类重要的功能材料.有机铁电体由于具有结构易剪裁,环保,随用随丢,易于生长高质量的晶体,尤其是易于和有机材料整合等特点, 开始引起广泛关注. 从铁电性产生的基本原理出发设计及可控合成获得铁电体将是今后寻求新的铁电体的一个重要方向.开展有机铁电体的可控制备,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。本项目在过去研究有机氢键型铁电体的基础上,拟采用类1,4-二氮杂二环[2.2.2]辛烷(dabco)和吡嗪的衍生物为分子构筑块，通过部分质子化可控合成获得一维氢键链结构, 通过砌块上不对称的取代基控制晶体堆积在铁电空间群,利用双稳态的氢键获得铁电性, 并对其结构、铁电、介电与压电,SHG相应等性质进行系统深入的研究. 结合朗道相变理论及第一性原理量化计算,深入探讨该类铁电体的铁电机理,发展分子基铁电物理学.

铁电体是一类重要的功能材料，可用作介电材料，存储材料，压电材料，热释电材料，光学材料，光伏材料。基于有机分子的铁电体由于具有结构易剪裁,环保,随用随丢,易于生长高质量的晶体,尤其是易于和有机材料整合等特点, 开始引起广泛关注. 本项目就是在这样的背景及过去的研究基础上开展的..通过可控制的合成，构建了一系列的氢键型化合物及其他基于有机分子的晶态化合物，通过示差扫描量热分析（DSC），变温二阶非线性（SHG）活性分析，变温介电谱测量，以及变温单晶结构分析等方法，发现了数个相变化合物。对于介电显著的晶体材料，进一步培养生长大的单晶，进行铁电性相关的表征，如测量电滞回线，测量热释电效应，观察畴结构等，从中筛选铁电相变。 通过综合分析结构和物理性质，达到认识铁电机理，评估铁电性能及应用前景，了解调节铁电性能的方法等目的，构成一个可控合成功能材料的系统和创新性的研究。其主要成果有(1) （1）构建了氢键型有机-无机金属卤素铁电化合物(3-Pyrrolinium)(CdCl3)，确认了分子铁电材料的反常光伏效应。 为制备高光伏电压的分子材料提供了新思路， 该成果发表在德国应用化学上。（2）深入研究了[(2,6-Diisopropylanilinium)([18]crown-6)]BF4的铁电性和铁电机理， 发现其不同于其他转子型铁电材料的机理，为设计新的分子离子型铁电体提供了新的思路。该成果发表在美国化学会志上。（3）合成了位移型金属-冠醚铁电体。确认了配位扭曲在分子基化合物中能导致铁电性。该发现对认识分子铁电和配位化学具有重要的贡献，发表在德国应用化学（Angew. Chem. Int. Ed.）。总统来说，该项目是顺利完成。