CAREER: SusChEM: Dynamic Defect Interactions in Ferroelectrics

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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.