多极轴分子铁电体的畴工程初步探索

Molecular ferroelectric materials are highly desirable for their easy processing, environmental friendliness, low cost, good biocompatibility and mechanical flexibility. The introduction of multiaxial characteristic will give rise to a class of polycrystalline materials in molecular ferroelectric systems, which can inherit the excellent ferroelectric properties and wide application of inorganic ferroelectrics, as well as the environmental friendliness, energy saving and multifunctional characteristics of molecular ferroelectrics. This project intends to synthesize a series of classically high-performance multiaxial molecular ferroelectric materials, and then observe the formation of ferroelectric domain structure during the phase transition process and the whole dynamic process of polarization switching under the application of external electric field in their different forms. Through systematic study of microscopic domain information, we can deeply understand the macroscopic ferroelectric properties, and construct the relationship between the structure and performance of molecular ferroelectrics. Subsequently, a practical and feasible solution would be established to improve performance. Finally, combined with precise chemical modifications, a series of multiaxial molecular ferroelectrics with excellent performances can be designed and developed, which would expand the polycrystalline molecular ferroelectric material system and play a significant role in promoting their device applications.

分子铁电材料因为有着易于加工、环境友好、成本低、生物相容性高和机械灵活性等诸多特性，已经成为当前的研究热点。把多极轴特性引入到分子铁电体中，将在分子铁电体系中催生出一类多晶态材料，在继承无机铁电体的优异性能和广泛应用的同时，又兼具分子铁电体独特的环保、节能以及功能特性易调控等优点。本项目拟通过合成制备经典的高性能多极轴分子铁电材料，在不同形态下原位观测铁电畴结构在相变过程中的形成以及在外电场作用下实现极化翻转的整个动力学过程。通过系统研究微观的畴信息来深入理解宏观的铁电压电性能，构筑分子铁电体的结构与性能之间的构效关系，从而建立一套切实可行的提高性能的方案。最终结合精准的化学修饰，优化改善设计出一系列性能优异的多极轴分子铁电体，拓展多晶态分子铁电材料体系，为早日实现器件化应用起到积极的推动作用。

分子铁电体的多极轴特性不仅可以带来独特的涡旋拓扑畴结构，而且可以使其能够应用于多晶态的薄膜和粉末，相对于单晶来说具有成本低廉、制备简单、形状可调等优点，可以推动分子铁电体的实际应用。本项目按项目任务书中内容计划实施，围绕多极轴分子铁电体研究，取得的重要研究成果包括：1.合成了系列具有涡旋拓扑畴结构的多极轴分子铁电体，研究了电畴结构与对称性破缺之间的关系。2.通过氟代效应设计了多极轴分子铁电体，其宏观铁电性可以以粉末压片和薄膜形式实现，氟代作用不仅增加了自发极化，还降低了矫顽场。3.构筑了单组分有机铁电晶体，通过光异构化引发的铁电结构相变实现光操控极化翻转。4.发现了系列单极轴分子铁电体，包括一维和三维有机-无机卤化物，并且通过氟代效应实现了相变温度的提高。在该项目的资助下，项目负责人以通讯或第一作者身份发表了 SCI 论文 13 篇，其中影响因子大于 3.0 的文章 13 篇， 包括 J. Am. Chem. Soc. 8 篇、 Adv. Mater.、Chem. Mater.、APL Mater.、Mater. Chem. Front.和Inorg. Chem. Front.各1篇，其中2篇被选为JACS Spotlights进行重点报道，1篇入选“ACS Editors’ Choice”。项目负责人入选了 2020 年度教育部“长江学者” 青年学者奖励计划和中国科协第六届青年人才托举工程。