Basic Research in Antiferroelectric Perovskites

9988853Chen本方案的目的是研究反铁电钙钛矿的基本材料问题。反铁电钙钛矿是铁性钙钛矿的一小部分。与典型的铁电钙钛矿相比，到目前为止，它们的应用相对有限，过去对它们的研究也少得多。然而，理论考虑表明，反铁电态在能量上类似于铁电态，并且在许多大响应铁电材料中存在着强烈的反铁电/铁电竞争，这是后者突出性质的核心。此外，几乎所有反铁电钙钛矿的几个共同的物理和化学特征，如负转变体积和非常弱的同位素效应，都是反常的，在任何铁电钙钛矿中都没有发现。这表明，反铁电钙钛矿的新基础研究将对用于重要技术和生物医学应用的铁电材料产生根本性影响。它还有可能发现具有诱人的物理和化学性质的新型铁电和反铁电体。在这个研究项目中，PI将确定反铁电-铁电转变的机械和电场效应，询问反铁电钙钛矿的局域原子和电子结构，并研究反铁电薄膜和异质结构。利用晶体化学和统计物理中的概念，实验将被设计来优化反铁电相互作用，并调整它们与铁电相互作用的竞争。同步加速器X射线和其他散射和成像技术将被用来探测可能导致反铁电性观察到的反常特征的阳离子耦合和电子跃迁。这项研究将由体相和薄膜反铁电体的性质表征进一步补充，以了解最小长度尺度上的相变、界面运动、界面-缺陷相互作用和反铁电/铁电竞争的热力学和动力学。反铁电钙钛矿是一种应用相对有限的钙钛矿，过去对它的研究要少得多。然而，理论考虑表明，这些材料可能具有独特的性质，因此对它们的基础研究将对用于重要技术和生物医学应用的铁电材料产生根本性的影响。该项目将培训博士生，并为本科生和高中教师提供培训。这一努力将纳入研究项目，以吸引传统和非传统学生，并为他们提供实验室和研究机会。

9988853ChenThe objective of this proposal is to investigate fundamental materials problems concerning antiferroelectric perovskites. Antiferroelectric perovskites are a small subclass of ferroic perovskites. Compared to prototypical ferroelectric perovskites, they have relatively limited applications to date and have been much less studied in the past. Nevertheless, theoretical considerations indicate that the antiferroelectric states are energetically similar to the ferroelectric states, and that in many large-response ferroelectrics there is a strong antiferroelectric/ferroelectric competition that is central to latter's outstanding properties. Moreover, several physical and chemical features common to nearly all of the antiferroelectric perovskites, e.g., a negative transformation volume and a very weak isotope effect, are anomalous and not found in any ferroelectric perovskites. This suggests that new basic research on antiferroelectric perovskites will have a fundamental impact on ferroelectrics that are used for important technological and biomedical applications. It also has the potential of discovering novel ferroelectrics and antiferroelectrics with attractive physical and chemical properties. In this research project, the PI will determine mechanical and electrical field effects on antiferroelectric-ferroelectric transitions, interrogate local atomic and electronic structures of antiferroelectric perovskites, and investigate antiferroelectric thin films and heterostructures. Using concepts in crystal chemistry and statistical physics, experiments will be designed to optimize antiferroelectric interactions and tune their competition with ferroelectric interactions. Synchrotron x-ray and other scattering and imaging techniques will be used to probe the cation couplings and electronic transitions that may give rise to the anomalous features observed in antiferroelectricity. This study will be further complemented by property characterization of bulk and thin film antiferroelectrics to understand the thermodynamics and kinetics of phase transitions, interface motion, interface-defect interactions, and antiferroelectric/ferroelectric competition at the smallest length scale. Antiferroelectric perovskites are a type of perovskites that have had relatively limited applications to date and have been much less studied in the past. Nevertheless, theoretical considerations indicate that these materials may have unique properties and thus basic research on them will have a fundamental impact on ferroelectrics that are used for important technological and biomedical applications. The project will train Ph.D. students as well as offering training to undergraduates and high school teachers. This effort will be integrated into the research project to attract traditional and non-traditional students and to provide them laboratory and research opportunities.