CAREER: Tuning Complexity in Rare-Earth Transition Metal Oxides

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。非技术性材料被称为复合氧化物，对于手机电池、各种电子设备中的电容器以及清除工业污染物的催化剂等技术来说是必不可少的。这些材料含有氧气和两种或两种以上的金属离子。这种构型允许高度可变的组成(存在哪些离子)和结构(离子如何排列)，这可以被利用来改进依赖这些化合物家族的技术。有了这个职业奖，田纳西诺克斯维尔大学的凯瑟琳·佩奇教授将研究含有五个或更多稀土元素或过渡金属离子的“高熵氧化物”(HEO)，这可以提供极其广泛的组成和结构。通过使用新的技术来发现和影响各种HEO原子的相互作用，这项研究将揭示如何将多种理想的物理性质结合到单一材料中。这些见解将导致更高效、更强大、更多样化的燃料电池、催化剂、传感器和电子产品。此外，该项目将制作一个中学研讨会系列，通过庆祝材料工程和结晶学的创造性探索过程的动手活动，促进材料化学和相关领域的职业生涯。参与这项研究的教授、研究生和本科生将在田纳西州和阿巴拉契亚农村社区的经济困难学校教授和指导研讨会系列的参与者。技术摘要田纳西诺克斯维尔大学的凯瑟琳·佩奇教授获得了这个职业奖项，旨在揭示在烧绿石和层状钙钛矿基稀土过渡金属络合物氧化物家族中实现分层和定制设计的规则，每个晶格位置具有两到五种原子类型。目前，人们对将传统的复杂氧化物相与新兴的高熵氧化物(每个晶格位置涉及五个或更多离子的材料)进行区分的分类知之甚少，包括需要在多大程度上使用新的设计范式来理解和控制其物理性质。高熵和动力学反应控制将研究它们在焦绿石族中生产单相材料和特定晶体化学条件的潜力，寻求在较低工作温度下改善离子传导性，以便在固体氧化物燃料电池和催化剂中潜在应用。类似的方法将寻求调整层状钙钛矿家族中的磁性、电子和多铁性响应。复杂的散射探头、理论工具和多模式建模方法将结合在一起，以评估局部到远程结构特征对各自系列的电子和磁性的影响。将确定特定缺陷、扭曲和化学短程有序可以实现和调整的程度，以影响结构类别的稳定性和各自的性质。这种基本的材料化学方法将导致设计具有所需特性组合的HEO材料所需的基本见解。从这项工作中产生的管理HEO稳定性、局部到全局对称性和整体可调性的关系将影响跨多个学科和应用展开的复杂氧化物化学的更广泛探索。同时，该项目将通过外展、教学和指导活动促进新一代科学家的发展，这些活动庆祝材料化学和结晶学方法的创造性探索过程，这是为东田纳西州和阿巴拉契亚社区经济困难中学的传统边缘群体举办的一系列研讨会的一部分。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).NON-TECHNICAL SUMMARYMaterials called “complex oxides” are essential for technologies such as cell phone batteries, capacitors in all kinds of electronic devices, and catalysts that clean up industrial pollutants. These materials contain oxygen and two or more types of metal ions. This configuration allows for highly variable composition (which ions are present) and structure (how the ions are arranged), which can be harnessed to improve the technologies that rely on these families of compounds. With this CAREER award, Professor Katharine Page at the University of Tennessee Knoxville will study “High Entropy Oxides” (HEOs) that contain five or more ions of rare-earth elements or transition metals, which can provide an extremely vast array of compositions and structures. By using novel techniques to uncover and influence how the various HEO atoms interact, this research will reveal how to combine multiple desirable physical properties into a single material. These insights will lead to more efficient, more powerful, and more diverse fuel cells, catalysts, sensors, and electronics. Additionally, this project will produce a middle school workshop series that will promote careers in materials chemistry and related fields through hands-on activities that celebrate the creative exploration process of materials engineering and crystallography. Professors, graduate students, and undergrads involved in the research will teach and mentor participants in the workshop series at economically disadvantaged schools in rural East Tennessee and Appalachian communities.TECHNICAL SUMMARY With this CAREER award, Professor Katharine Page at the University of Tennessee Knoxville aims to uncover the rules for enabling hierarchical and tailored design in pyrochlore and layered perovskite-based rare earth transition metal complex oxide families featuring two to five atom types per lattice site. Relatively little is currently known about the classifications separating traditional complex oxide phases from the emerging class of High Entropy Oxides (materials involving five or more ions per lattice site), including the extent to which new design paradigms are needed to understand and control their physical properties. High entropy and kinetic reaction controls will be examined for their potential to produce single-phase materials and specific crystal-chemical conditions in the pyrochlore family, seeking to improve ionic conductivity at lower working temperature for potential applications in solid oxide fuel cells and catalysts. Similar approaches will seek to tune magnetic, electronic, and multiferroic responses in the layered perovskite family. Sophisticated scattering probes, theoretical tools, and multi-modal modeling methods will be combined to evaluate the impact of local to long-range structure traits on the electronic and magnetic properties of the respective series. The extent to which specific defects, distortions, and chemical short-range order may be achieved and tuned to impact the stability and respective properties of the structural classes will be determined. This fundamental materials chemistry approach will lead to the foundational insights necessary to design HEO materials with desired combinations of traits. Relationships governing the stability, local to global symmetry, and overall tunability in HEOs emerging from this work will impact the broader exploration of complex oxide chemistries unfolding across multiple disciplines and applications. Concurrently, this project will promote a new generation of scientists through outreach, teaching, and mentoring activities that celebrate the creative exploration process of materials chemistry and crystallography approaches as part of a workshop series for traditionally marginalized groups at economically disadvantaged middle schools in rural East Tennessee and Appalachian communities.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.