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

非技术概要：电致伸缩器将电能转化为机械能，而不是反之。这种机电转导的结构基础与压电材料有着根本的不同，压电材料可以实现电能到机械能的转换，反之亦然。NCES效应，最近由首席研究员（PI）， A. Frenkel（美国石溪大学）和外国合作者（FC）， I. Lubomirsky（以色列魏茨曼研究所）在zr - zno氧化铈中发现，导致比经典电致伸缩器预测的更大（两个或更多数量级）的变形响应于外加电场。具体来说，虽然目前商业上使用的电致伸缩器是基于铅的，但新发现的成分是完全无毒的。相反，与之前报道的NCES案例相比，新发现的材料没有局部弹性偶极子，这是单位胞内的永久扭曲，破坏了整体对称性。相反，新发现的材料中的扭曲是动态的，这清楚地表明以前未知的NCES机制正在起作用。该团队将研究这类材料（Zr和Hf掺杂的铈）的电致伸缩的起源，采用先进的时间分辨技术，基于同步加速器x射线吸收光谱，由PI执行，机电测量，由FC执行，FC也将合成样品。该项目将利用美国PI的专业知识，使用先进的原子和结构表征功能材料，与以色列合作者的专业知识，陶瓷的制备和机械性能。该团队将通过时间分辨方法检测偶极子对变化电场的动态响应，在有电场和没有电场的情况下，对Zr （Hf）和Ce原子的局部环境进行原子级表征。该项目将产生四个重要成果：(1)获得了具有动态弹性偶极子的NCES的基本描述子；(2)为NCES效应的理论建模提供了基础；(3)培养了新一代材料科学专业的研究生和本科生在大型用户设施中实践先进表征方法；(4)建立石溪大学与魏茨曼科学研究所师生科研团队国际合作项目框架。技术总结：在过去的十年中，在首席研究员A. Frenkel（美国石溪大学）和外国合作者I. Lubomirsky（以色列魏茨曼研究所）的合作下，发现了非经典电致缩效应（NCES）。这些材料的电伸缩系数比经典标度定律预测的高两个数量级以上，与以前在离子导体中观察到的相似。NCES最初是在非常低的频率下检测到的，产生非常小的变形（几ppm），并且归因于由点缺陷、氧空位或质子间隙引起的弹性偶极子。PI和FC的团队最近发现了一种材料，锆掺杂的氧化铈，其NCES在所有实际参数上都可以与商业上使用的电致伸缩器相媲美：数百ppm的应变，大弹性模量和khz范围的响应。因此，这些特性，除了新组合物完全无毒的突出优势外，有望取代商业铅基电致伸缩器。这种材料不含有大量的空位或间隙，因此不具有永久的弹性偶极子，这清楚地表明NCES的一种以前未知的机制正在起作用。该项目将利用美国首席研究员在使用功能材料的先进原子和结构表征方面的专业知识，以及以色列合作者在陶瓷制备和机械性能方面的专业知识。该项目的最终目标是在存在和不存在外部外加电场的情况下，对NCES的局部离子环境进行原子水平表征。同步加速器表征的时间分辨方法在这方面具有独特的吸引力，因为它们捕捉到化学碳中特定元素的变化。该项目将产生四个重要成果：(1)获得了具有动态弹性偶极子的NCES的基本描述子；(2)为NCES效应的理论建模提供了基础；(3)培养了新一代材料科学专业的研究生和本科生在大型用户设施中实践先进表征方法；(4)建立石溪大学与魏茨曼科学研究所师生科研团队国际合作项目框架。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.