NSF/DMR-BSF: Origin of Large Electromechanical Response in Non-Classical Electrostrictors

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NON-TECHNICAL DESCRIPTION: Materials with strong mechanical response to applied electric field are of great importance for a wide range of applications ranging from actuators for portable cameras to transducers for audio-speakers and sonars. Since discovery of a giant electromechanical response in gadolinium-doped cerium oxides in 2012, this material is considered as a new type of ceramic that generates strain due to a small fraction of their structural units, called electromechanically "active". The main challenge towards understanding this mechanism and rational designing new electromechanical materials with the desired response has been the inability to decipher atomic architecture of these units and "catch them in action", that is, to take a snapshot of these units while the strain is generated under electric field. In order to fully characterize the structure of active units "in action", the investigators are studying thin film doped cerium oxide ceramics under electric field by high energy resolution methods (such as X-ray absorption spectroscopy) and modeling the results by advanced theoretical methods. The project impacts the field of ceramic materials through the development of fundamental understanding and design criteria for this new class of electromechanical materials. The project fosters international ties between Yeshiva University in New York and Weizmann Institute of Science in Rehovot, Israel. The broader impacts of this project are realized through establishing connections between faculty and students from both institutions, and in engaging underrepresented groups (such as women) in science and engineering disciplines. TECHNICAL DETAILS: Thin films of cerium oxide that have trivalent metal impurities possess intriguing structural, electric and mechanical properties, including ionic conductivity, non-linear elastic effects and strong mechanical stresses in response to the application of electric field. Anatoly Frenkel (SUNY at Stony Brook), his international collaborator Igor Lubomirsky (Weizmann Institute of Science) and their respective groups are working to understand the mechanisms of electrostriction (a particularly large electromechanical response that is quadratic with electric field). The investigators strive to answer such fundamental questions as the effects of impurities on the generation of strain and stress in the lattice. They are applying advanced methods of X-ray absorption spectroscopy with high energy resolution in situ, under applied field, to identify the active species - cations that are located in the distorted units - in order to understand, in detail, the behavior of these units and their role in the electrostriction. Data analysis is being carried out by modeling structural distortions theoretically and comparing their simulated X-ray absorption spectra with experimental ones. This project offers research opportunities and training at advanced national research facilities at the post-graduate, graduate and undergraduate levels with significant inclusion of underrepresented female students.