CAREER: Dynamic Point Defect Architectonics - Uncovering Crystal Chemical Design Rules for Tailored Chemical Expansion

非技术描述：许多陶瓷材料“呼吸”-它们可以与周围的气体交换，例如氧气或水，从而导致其尺寸的变化。当脆性陶瓷被限制在传感器、反应堆、电池和燃料电池等设备中时，这种拉伸会给它们的耐用性带来问题：它会导致裂缝和断裂。另一方面，这种“呼吸”行为提出了开发一种新应用的可能性：用于极端环境的致动器。此外，在过去的5-10年里，利用这种行为的先进材料表征技术已经出现。因此，这是一个很好的时间来测量和了解呼吸更全面，并研究如何设计材料与控制尺寸变化。该项目专注于技术上重要的一类陶瓷，称为钙钛矿，并试图了解它们在局部电荷、原子和键排列水平上的结构如何影响它们在呼吸过程中大小的变化。关于如何调整这些材料的局部结构以控制膨胀量，实验正在测试三个具体的想法。学生们正在接受训练，使用精确的膨胀测量、先进的显微镜技术和国家实验室提供的强光源，观察许多长度尺度上的拉伸。预期的结果是如何设计具有更好耐用性的陶瓷，用于能量转换和存储应用，以及为新型执行器和优化测量量身定制响应。这些研究工作与教育方法相结合，包括对日本的国际交流访问，这将培养学生成为清晰的沟通者，跨文化敏感性，计算和实验素养，并推动深度学习。一个新的夏令营模块链接到可持续能源的研究应用。它旨在通过干预高中水平，鼓励代表性不足的群体参与本科水平的材料科学，以增加学生的信心、动力和自我效能感。技术细节：该项目旨在建立混合和质子导电钙钛矿氧化物中键结构、局部点缺陷引起的扭曲和宏观化学引起的应变之间的定量关系。点缺陷控制着技术陶瓷的行为，这项工作对缺陷结构及其在化学-机械耦合中的作用的洞察将有助于“缺陷基因组”的发展。包括膨胀测量法、原位衍射、热重分析、先进的电子显微镜、x射线吸收和散射等方法被用于量化化学计量学变化、缺陷引起的局部扭曲和宏观应变。其结果将是建立适合化学膨胀系数的晶体化学设计规则。这些规律可以应用于提高陶瓷在能量转换、存储、传感和驱动应用中的耐久性和优化响应。此外，学生不仅将在大学和国家实验室环境中接受技术技能的培训，还将在全球范围内接受各种更广泛的专业技能的培训。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 DESCRIPTION: A number of ceramic materials “breathe” – they can exchange, e.g., oxygen or water, with the gas around them, causing a change in their size. This stretching of the brittle ceramics can cause problems for their durability when they are constrained in devices, such as sensors, reactors, batteries, and fuel cells: it can cause cracks and fracture. On the other hand, this “breathing” behavior raises the possibility to develop a new application: actuators for use in extreme environments. Additionally, over the past 5-10 years, advanced materials characterization techniques that leverage this behavior have emerged. Therefore, it is an excellent time to measure and understand the breathing more completely and to investigate how to design materials with controlled size changes. This project focuses on a technologically important class of ceramics, called perovskites, and seeks to understand how their structure at the level of local charge, atom, and bond arrangements impacts how they change size during breathing. Experiments are testing three specific ideas about how the local structure of these materials can be tailored to control the amount of expansion. Students are being trained to observe the stretching across many length scales, using precise expansion measurements, advanced microscopy techniques, and the intense light sources available at national laboratories. The expected outcome is knowledge of how to design ceramics with better durability for energy conversion and storage applications and tailored responses for novel actuators and optimized measurements. These research efforts are integrated with educational approaches including international exchange visits to Japan, which train students to be clear communicators, cross-culturally sensitive, both computationally and experimentally literate, and motivated toward deep learning. A new summer camp module links to the research applications in sustainable energy. It aims to encourage participation of under-represented groups in materials science at the undergraduate level by intervening at the high school level to increase students’ confidence, motivation, and self-efficacy.TECHNICAL DETAILS: The project seeks to establish quantitative relationships between bond architecture, local point defect-induced distortions, and macroscopic chemically-induced strain in mixed- and proton-conducting perovskite oxides. Point defects govern the behavior of technical ceramics, and this work’s insight into the structure of defects and their role in chemo-mechanical coupling will add to the development of the “defect genome.” Methods including dilatometry, in situ diffraction, thermogravimetric analysis, advanced electron microscopy, and X-ray absorption and scattering, are being used to quantify stoichiometry changes, defect-induced local distortions, and macroscopic strain. The outcome will be the establishment of crystal chemical design rules for tailored coefficients of chemical expansion. These rules can be applied to improve durability and optimize responses of ceramics in energy conversion, storage, sensing, and actuation applications. Additionally, students will be trained in not only technical skills in university and national laboratory settings, but also in a variety of broader professional skills in a global context.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.