CAREER: SusChEM: Dynamic Defect Interactions in Ferroelectrics

非技术描述：所有陶瓷都含有缺陷、杂质和界面；这是不可避免的。几十年来，人们一直在研究缺陷对性能的影响，但之前的大部分工作都集中在静态或稳态条件上。铁电材料(具有可通过电场重新定向的永久偶极的材料)和压电材料(施加机械应力时会产生电荷的材料)在各种应用中都很重要，从有助于在较小的电子设备中填充更多功能的存储设备和电容器，到提高汽车燃油经济性的致动器和收集环境振动能量的设备。这些类型的材料通常在动态条件下使用，在动态条件下，移动的域壁主导属性响应。该项目利用新的实验技术和独特的样本集来改进对这些移动的磁场壁与无处不在的点缺陷和界面(如空位和晶界)相互作用的定量描述。通过更好地了解域壁与缺陷和界面的相互作用，可以通过无铅压电材料和不含有毒或贵金属的高价值催化剂的主动控制来提高性能，从而使用更可持续的材料来生产有助于提高各种行业的能效和工艺可持续性的设备。该项目与派？S的广泛努力相结合，以扩大学生的参与度，包括参加一年一度的发现STEM！夏令营，课程开发，以及校园内一家热玻璃店的介绍。学生交换协议允许受资助的研究生每年与弗吉尼亚州和澳大利亚的合作者一起工作数周，利用这些小组中可用的工具和专业知识，同时受益于在不同环境中生活和工作的经验。技术细节：这项工作将目前用于描述磁区成核和钉扎过程的抽象能垒与真实的化学和/或结构特征联系起来，以便识别和概括各种特征作为成核和/或钉扎点的条件。样本集和实验分离变量(例如，分别与阳离子空位和晶界的磁畴壁相互作用)，并应用新的工具，包括原子探针和X射线层析、时间域热反射和定制的低阻抗驱动电路，以开发将广泛应用于许多材料家族的磁畴成核和钉扎的基本机制描述。

NON-TECHNICAL DESCRIPTION: All ceramics contain defects, impurities, and interfaces; this is simply unavoidable. Decades of work have gone into understanding the effects of defects on properties, but the vast majority of this prior work has focused on static or steady-state conditions. Ferroelectrics (materials with a permanent dipole that can be reoriented by an electric field) and piezoelectrics (materials that develop an electric charge when a mechanical stress is applied) are important for applications ranging from memory devices and capacitors that help cram more features into smaller electronic devices to actuators that increase automotive fuel economy and devices that harvest ambient vibrational energy. These types of materials are commonly used under dynamic conditions in which moving domain walls dominate the property responses. This project uses new experimental techniques and unique sample sets to improve the quantitative descriptions of the interactions of these moving domain walls with ubiquitous point defects and interfaces such as vacancies and grain boundaries. Better understanding of domain wall interactions with defects and interfaces enables improved performance from Pb-free piezoelectrics and active control of high-value catalysts which are free of toxic or precious metals, thus using more sustainable materials to produce devices that contribute to increased energy efficiency and process sustainability across a variety of industries. The project integrates with the PI?s extensive efforts to expand student engagement including participation in an annual Discover STEM! Camp, curriculum development, and introduction of a hot glass shop on campus. A student swap agreement allows the supported graduate student to work for several weeks each year with collaborators in Virginia and Australia, taking advantage of the tools and expertise available in those groups while benefitting from the experience of living and working in a different environment.TECHNICAL DETAILS: This work links the abstract energy barriers currently used to describe the domain nucleation and pinning processes to real chemical and/or structural features in order to identify and generalize the conditions under which various features serve as nucleation and/or pinning sites. The sample sets and experiments isolate variables (e.g., domain wall interactions with cation vacancies and with grain boundaries separately) and apply new tools including atom probe and X-ray tomographies, time domain thermal reflectance, and a custom low-impedance drive circuit to develop fundamental mechanistic descriptions of domain nucleation and pinning that will apply broadly across many materials families.