Manipulation of perovskite dielectrics with high electric fields and large strains

非技术描述：在电子、传感和清洁能源的应用中，实现材料的精确、可重复和动态可调控制是一个持久而重要的挑战。电场在这方面可能是有用的，因为它们可以在这些材料的电子和结构性质上产生巨大和令人惊讶的变化。新技术已经能够在不破坏薄层的情况下将大电场施加到非常薄的层上，产生巨大但尚不清楚的效果。本项目研究基于金属复合氧化物的一类特殊材料在薄膜中引起的结构变化。正在使用X射线散射进行实验，精确地描述应用领域中的晶体结构。本科生和研究生参与国家X射线散射设施的实验，并使用理论计算解释实验结果。基于本项目概念的推广活动将与电场如何改变材料的原子级结构相关的概念带给广泛的受众，包括通过创建在线结构模型。技术细节：强电场有望在研究并最终控制和利用钙钛矿氧化物材料中的结构现象方面提供新的自由度。高电场有可能诱导结构相变，改变结构对称性，并增加电致伸缩的重要性，而在低电场下，电致伸缩的影响可以忽略不计。本项目使用最新开发的时间分辨X射线微衍射表征技术来探索钙钛矿复合氧化物在高电场和大应变下的性质。实验正在研究最近报道的三方相和四方相之间的电场驱动结构相变的动力学，探索超晶格中压电性和晶体对称性之间的关系，以及探索复杂氧化物介质中电致伸缩变形的极限。该项目正在为本科生和研究生在科学和技术领域的职业生涯做准备，并让他们接触到国家X射线散射设施的研究。这些复杂氧化物材料的原子结构和本项目中研究的结构现象通过一系列交互式在线结构模型向广大观众展示。

NON-TECHNICAL DESCRIPTION:It is a persistent and important challenge to achieve precise, reproducible, and dynamically adjustable control of materials with applications in electronics, sensing, and clean energy. Electric fields can be useful in this respect because they can produce dramatic and surprising changes in the electronic and structural properties of these materials. New technologies have resulted in the capability to apply large electric fields to very thin layers without destroying them, yielding large but not yet understood effects. This project probes the structural changes induced in thin films of a particular class of materials based on metal complex oxides. Experiments are being conducted using X-ray scattering, precisely characterizing the crystallographic structure in applied fields. Undergraduates and graduate students are involved in experiments at national X-ray scattering facilities and in the interpretation of the experimental results using theoretical calculations. Outreach activities based on the concepts in this project bring concepts related to how the atomic-scale structure of materials is modified by electric fields to wide audiences, including through the creation of on-line structural models.TECHNICAL DETAILS:High electric fields promise to provide a new degree of freedom in studying and ultimately controlling and exploiting structural phenomena in perovskite oxide materials. High fields have the potential to induce structural phase transitions, to modify the structural symmetry, and to increase the importance of electrostriction, a largely negligible effect at low electric fields. This project uses newly developed time-resolved X-ray microdiffraction characterization techniques to probe the properties of perovskite complex oxides in high electric fields and at large strains. Experiments are underway to examine the dynamics of recently reported electric-field-driven structural phase transitions between rhombohedral and tetragonal phases, probe the relationship between piezoelectricity and crystallographic symmetry in superlattices, and explore the limits of electrostrictive distortion in complex oxide dielectrics. The project is preparing undergraduates and graduate students for careers in science and technology and exposing them to research at national X-ray scattering facilities. The atomic structure of these complex oxide materials and the structural phenomena studied in this project are presented to broad audiences using a series of interactive on-line structural models.