NSF-BSF: Descriptors of Dynamic Elastic Dipoles in Non-Classical Electrostrictors

NON-TECHNICAL DESCRIPTION: Materials that can undergo large changes in shape when an electric field is applied are very important for many essential technologies—from everyday items like cellphones and washing machines to advanced automotive systems. Among these materials, electrostrictors have attracted growing interest in recent years. These materials are unique because they convert electrical energy into mechanical movement, but not the other way around. The project aims to understand the origin of the electrostriction effect in specific ceramic materials, where a few percent of foreign atoms with the same valency replacing the host atoms may be solely responsible for the field-induced volume change—and the resulting large strain. This insight opens a pathway to the rational design of lead-free alternatives to the dominant commercial electrostrictive ceramics. One of the main difficulties is the lack of methods for identifying the key features—called descriptors—of this effect and help predict which ceramic materials will exhibit this behavior. The project aims at developing a new idea for electrostrictive materials, using zirconium-doped cerium oxide. To explore how it works, X-ray absorption spectroscopy is used, a technique that uses very bright X-rays to track changes in the atomic environment around metal ions when conditions such as temperature, pressure, or electric field change. This work contributes to the field by improving understanding of this class of materials and helping predict new ones beyond cerium-based systems. Technologically, this new group of safe, electromechanically active materials could have wide applications. Students will also benefit through deeper learning in advanced topics in materials science, engineering, chemistry, and physics. TECHNICAL DESCRIPTION: The focus of this research project is the development of atomic-level understanding of new types of ceramic materials, those that combine large electrostrictive strain with low dielectric permittivity and high elastic modulus, thereby potentially making these materials attractive for many important applications. The electrostriction effect is the change in mechanical dimensions of a solid as a result of the application by an electric field but not vice versa. The PI and the international collaborator, Prof. Igor Lubomirsky (Weizmann Institute of Science, Israel), propose a new class of ceramic materials based on the Zr-doped ceria that do not have pre-existing elastic dipoles, yet are capable of generating strains up to 1000 ppm under applied field (as large as in the best commercial, lead-based, electrostrictors). To formulate the conditions for the rational search and design of other materials capable of exhibiting this electrostriction effect, the complex relationship between the descriptors of local structure and the dynamics of nearest neighbors surrounding the dopant (Zr) and the host (Ce) ion must be understood. Atomic-level synchrotron characterization performed under temperature, applied stress, or electric field conditions, provides insights into the effects of the separate responses of different components of this system and identifies the bond length mismatch and bond anharmonicity as likely candidates for electrostriction descriptors. This project offers research opportunities and training at advanced national research facilities at the post-graduate, graduate, and undergraduate levels. The project impacts the field of ceramic materials through the development of fundamental understanding and material selection rules for the new class of electrostrictive materials. 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.