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

点击翻译按钮获取中文摘要

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.