NSF-BSF: Electrostriction in Ceramic Materials with Dynamic Elastic Dipoles

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

NON-TECHNICAL SUMMARY: Electrostrictors convert electrical energy into mechanical energy but not vice versa. The structural basis for this electromechanical transduction is fundamentally different from piezoelectric materials, which enabled electrical to mechanical energy conversion and vice versa. The NCES effect, recently discovered by the principal investigator (PI), A. Frenkel (Stony Brook University, USA) and the foreign collaborator (FC), I. Lubomirsky (Weizmann Institute, Israel) in Zr-doped cerium oxide, results in much larger (by two or more orders of magnitude) deformation in response to an applied electric field than that predicted in classical electrostrictors. Specifically, while current commercially used electrostrictors are lead-based, the newly discovered compositions are completely nontoxic. In contrast, to the previously reported cases of NCES, the newly discovered materials do not have local elastic dipoles which are permanent distortions within the unit cells, breaking the overall symmetry. Instead, the distortions in the newly discovered materials are dynamic, clearly indicating that the previously unknown mechanism of NCES is at work. The team will investigate the origin of the electrostriction in this class of materials (Zr- and Hf- doped ceria) with advanced time-resolved techniques based on synchrotron X-ray absorption spectroscopy, performed by the PI, and electromechanical measurements, performed by the FC who will also synthesize the samples. This project will leverage the expertise of the US PI, in using advance atomistic and structural characterization of functional materials, with the expertise of the Israeli collaborator, in preparation and mechanical properties of ceramics. The team will perform atomic-level characterization of the local environment of Zr (Hf) and Ce atoms, with and without electric field, through time-resolved methods for detecting the dynamic response of the dipoles to the changing electric field. The project will have four important outcomes: (1) Obtaining the fundamental descriptors of NCES with dynamics elastic dipoles, (2) Providing basis for the theoretical modeling of the NCES effect, (3) Training a new generation of graduate and undergraduate students specializing in materials science on advanced characterization methods practiced at large user facilities, and (4) Establishing a framework of collaborative international projects connecting faculty-student research teams of Stony Brook University and Weizmann Institute of Science. TECHNICAL SUMMARY: During the last decade, the collaboration of the principal investigator (PI), A. Frenkel (Stony Brook University, USA) and the foreign collaborator (FC), I. Lubomirsky (Weizmann Institute, Israel), has led to the discovery of the non-classical electrostriction effect (NCES). These materials show an electrostrictive coefficient two or more orders of magnitude higher than predicted by the classical scaling law and similar to what previously observed exclusively in ionic conductors. NCES was originally detected at very low frequencies, produced very small deformation (few ppm), and was attributed to the elastic dipoles induced by point defects, oxygen vacancies or proton interstitials. The team of the PI and FC has recently discovered a material, Zr-doped cerium oxide, that exhibits NCES rivaling commercially used electrostrictors in all practical parameters: hundreds of ppm of strain, large elastic modulus, and kHz-range response. Therefore, such properties, in addition to the prominent advantage of the new composition to be completely nontoxic, promise a replacement of the commercial lead-based electrostrictors. This material does not contain significant concentration of vacancies or interstitials and, thereby, does not have permanent elastic dipoles, clearly indicating that a previously unknown mechanism of NCES is at work. This project will leverage the expertise of the US Principal Investigator in using advance atomistic and structural characterization of functional materials, with the expertise of the Israeli collaborator in preparation and mechanical properties of ceramics. The ultimate goal of the project is atomic-level characterization of the local ionic environment of the NCES, in presence and absence of an external applied electric field. Time-resolved methods of synchrotron characterization are uniquely attractive for this purpose because they capture the element-specific changes in the chemical bons. The project will have four important outcomes: (1) Obtaining the fundamental descriptors of NCES with dynamics elastic dipoles, (2) Providing basis for the theoretical modeling of the NCES effect, (3) Training a new generation of graduate and undergraduate students specializing in materials science on advanced characterization methods practiced at large user facilities, and (4) Establishing a framework of collaborative international projects connecting faculty-student research teams of Stony Brook University and Weizmann Institute of Science. 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.