Synthesis and Mechanistic Studies of New Series of Ferroelastic and Ferroelectric Crystals

现代晶体工程的主要目标之一是设计、合成和优化具有特定功能的新材料。该研究计划的重点是铁弹性和铁电畴开关的技术上有用的属性，其中晶体内的畴或区域的取向可以通过施加各向异性应力（铁弹性）或电场（铁电性）来改变。这种材料的合理设计（可以作为光门或存储器设备）需要更深入地了解域切换的机制，域切换是一种在分子，纳米和介观尺度上控制的可见的宏观现象。在铁弹性的分子决定因素的早期工作的基础上，这项工作将集中在一系列的铁弹性andferroelectric晶体中的畴变的机制研究，其中的合作，弹性障碍畴变和铁电有序可以优化和定制。由于可以产生和比较如此大量的密切相关的结构，因此它集中于一系列具有铁弹和/或铁电畴变的包合物、共晶和有机盐的设计、合成和机理研究。由于它们可以提供关于畴变势垒的见解，这项工作将利用各种技术（例如，X射线衍射、同步加速器白色束X射线形貌术、固态核磁共振、超快视频显微镜、双折射映射）来探测“记忆效应”或“橡胶样行为”现象，即由应力（或电场）产生的子域自发地回复到母取向。对这种记忆效应的更透彻的理解将有助于有针对性的和迭代的方法来形成一系列具有明确属性的铁电晶体。因为他们将被要求整合各种方法的结果，并利用这些结果在新材料的设计，这项研究计划将提供一个基础广泛的培训本科生，研究生和博士后学生谁将追求的职业生涯在materialschemes。通过整合一系列密切相关的结构上的大量实验结果，应该有可能开发一个更基本的理解的因素控制在各种铁电材料中的畴开关和记忆效应。这项工作将在论文和演示文稿中广泛传播，并在研究生课程和本科生实验室中使用。

One of the principal goals of modern crystal engineering is the design, synthesis and optimization of new materials with specified function. This research program focuses on the technologically useful properties of ferroelastic and ferroelectric domain switching, in which theorientations of domains or regions within a crystal can be changed by application of anisotropic stress (ferroelasticity) or electric fields (ferroelectricity). The rational design of such materials (which can act as light gates or memory devices) requires a deeper understanding of the mechanisms of domain switching, a visible, macroscopic phenomenon that is controlled at the molecular, nanoscopic and mesoscopic scales. Building upon earlier work on the molecular determinants of ferroelasticity, this work will focus on mechanistic studies of domain switching in series of ferroelastic andferroelectric crystals in which the cooperative, elastic barriers to domain switching and ferroelectric ordering can be optimized and tailored. Because such a large number of closely related structures can be generated and compared, it concentrates on the design, synthesis and mechanistic studies ofseries of inclusion compounds, co-crystals and organic salts that exhibit ferroelastic and/or ferroelectric domain switching.Because of the insights they can provide about the barriers to domain switching, this work will utilize a variety of techniques (e.g., X-ray diffraction, synchrotron white beam X-ray topography, solid state nuclear magnetic resonance, ultrafast videomicroscopy, birefringence mapping) to probethe phenomenon of "memory effects" or "rubber-like behavior," in which the daughter domain that is generated by stress (or electric field) spontaneously reverts back to the parent orientation. A more thorough understanding of such memory effects will facilitate a targeted and iterative approach toforming series of ferroelectric crystals with well-defined properties.Broader Impacts: Because they will be required to integrate results from various methods and to utilize these results in the design of new materials, this research program will provide a broad-based training for undergraduate, graduate and postdoctoral students who will pursue careers in materialschemistry. By integrating numerous experimental results on a series of closely related structures,it should be possible to develop a more fundamental understanding of the factors controlling domain switching and memory effects in a variety of ferroelectric materials. This work will be disseminatedwidely in papers and presentations and utilized in graduate-level courses and undergraduate laboratories.