Solid-State Oxides and Oxide-Fluorides

激光器是贝尔实验室的科学家于1960年发现的。在最初发现的一年后，一组研究人员证明，激光脉冲产生的高电场通过一种称为二次谐波产生的非线性光学（NLO）过程，将穿过石英晶体的光从一种颜色转换为另一种颜色（红色变为绿色）。从那时起，像石英这样的NLO材料在推进激光科学前沿方面发挥了关键作用。在非中心对称（NCS）固体中，反转对称性被破坏的材料允许具有NLO活性和其他激发性质。通过这个由美国国家科学基金会固态和材料化学项目支持的项目，西北大学的poepelmeier教授小组推进了对化学如何用于创建具有破逆对称性的材料以及将原子结构与性质联系起来的理解。各种合成方法被用来控制组成晶体结构的构建块的排列。他们生长的大型、高质量的NCS材料晶体使得详细研究NCS材料的原子结构和性能之间的联系成为可能。这项研究是由本科生和研究生进行的，他们在这个项目的过程中接受了最先进的固体化学训练。此外，学生们还被鼓励参加PI本人参与的无数的外展活动。技术摘要激光技术的进步导致激光系统在从眼科手术到粒子加速等领域的应用显著增加。新兴的激光技术需要能够通过非线性光学过程（如二次谐波产生和参数放大）有效转换激光辐射频率的高性能材料。在可调谐激光系统中应用所必需的NLO特性，以及其他技术上有用的特性，如压电性、铁电性和热电性，可以在缺乏反转对称性的晶体材料中获得，称为非中心对称（NCS）固体。该项目由美国国家科学基金会固态和材料化学项目支持，开发了针对NCS材料的合成方法，使用水热、溶剂热和固态方法来控制阴离子基本构建单元的排列，从而实现有用的性能。这些综合努力以化学知识和机器学习方法为指导，这些方法从大量实验数据中阐明重要趋势。大质量晶体的生长使得单晶和粉末x射线衍射以及NLO和其他性能测量能够进行结构表征，以确定结构-性能关系。对NCS材料的合成、结构和性能的研究有望导致新的NCS材料的发现和未来NCS材料合成的新策略。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical SummaryLasers were discovered in 1960 by scientists at Bell Laboratories. A year after the initial discovery, a group of researchers demonstrated that the high electric fields produced by a laser pulse converted the light passing through a quartz crystal from one color to another (red to green) via a nonlinear optical (NLO) process called second-harmonic generation. Since then, NLO materials like quartz have played a key role in advancing frontiers in laser science. NLO activity and other exciting properties are allowed in materials where inversion symmetry in broken, which are known as noncentrosymmetric (NCS) solids. Through this project, which is supported by the Solid State and Materials Chemistry program at NSF, Prof. Poeppelmeier's group at Northwestern University advances the understanding how chemistry can be used to create materials with broken inversion symmetry and connect atomic structure to properties. A variety of synthetic approaches are used to control the alignment of the building blocks that make up a crystal structure. Their growth of large, high-quality crystals of NCS materials enables detailed investigation of the connection between atomic structure and properties in NCS materials. The research is carried out by undergraduate and graduate students, who in the process of this project are trained in state-of-the-art solid state chemistry. Additionally, the students are encouraged to participate in a myriad of outreach activities that the PI himself is involved in.Technical SummaryAdvances in laser technology have led to a significant increase in the application of laser systems in areas ranging from eye surgery to particle acceleration. Emerging laser technologies require high-performance materials that can efficiently convert the frequency of laser radiation through nonlinear optical (NLO) processes, such as second-harmonic generation and parametric amplification. The NLO properties necessary for applications in tunable laser systems, as well as other technologically useful properties such as piezoelectricity, ferroelectricity, and pyroelectricity, are available in crystalline materials lacking inversion symmetry, known as noncentrosymmetric (NCS) solids. This project, which is supported by the Solid State and Materials Chemistry program at NSF, develops targeted synthesis methods for NCS materials using hydrothermal, solvothermal, and solid-state methods to control the alignment of anionic basic building units such that useful properties can be realized. These synthetic efforts are guided by chemical knowledge as well as machine learning methods that elucidate important trends from large amounts of experimental data. The growth of large, high-quality crystals enables structural characterization with single crystal and powder x-ray diffraction along with NLO and other property measurements to determine structure-property relationships. Examination of the syntheses, structures, and properties of NCS materials is expected to lead to discovery of new NCS materials and new strategies for future NCS materials synthesis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.