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

非技术描述：具有对外加电场的强烈机械响应的材料对于广泛的应用非常重要，从便携式相机的致动器到音频扬声器和声纳的换能器。自从2012年在掺Gd的CeO2中发现了巨大的机电响应以来，这种材料被认为是一种新型陶瓷，由于其结构单元中的一小部分而产生应变，被称为机电“活性”。理解这一机制和合理设计具有所需响应的新机电材料的主要挑战是无法破译这些单元的原子结构并“捕捉它们的作用”，即在电场下产生应变时拍摄这些单元的快照。为了充分表征活性单元的结构，研究人员正在利用高能量分辨方法(如X射线吸收光谱)在电场作用下研究薄膜掺杂氧化铈陶瓷，并用先进的理论方法对结果进行模拟。该项目通过对这种新型机电材料的基本理解和设计标准的发展，对陶瓷材料领域产生了影响。该项目促进了纽约耶希瓦大学和以色列雷霍沃特魏兹曼科学研究所之间的国际联系。该项目的更广泛影响是通过在这两个机构的教职员工和学生之间建立联系，以及在科学和工程学科中吸收代表性不足的群体(如妇女)来实现的。技术细节：含有三价金属杂质的氧化铈薄膜具有耐人寻味的结构、电学和机械性能，包括离子导电性、非线性弹性效应和响应于电场的强大机械应力。Anatoly Frenkel(Yeshiva大学)、他的国际合作者伊戈尔·卢博米斯基(魏茨曼科学研究所)和他们各自的团队正在努力了解电致伸缩(一种与电场平方的特别大的机电响应)的机制。研究人员努力回答这样的基本问题，如杂质对晶格中应变和应力的产生的影响。他们正在应用现场高能量分辨率的先进X射线吸收光谱方法，在外加电场下识别活性物种--位于扭曲单元中的阳离子--以便详细了解这些单元的行为及其在电致伸缩中的作用。数据分析是通过对结构变形进行理论建模，并将模拟的X射线吸收光谱与实验结果进行比较来进行的。该项目在研究生、研究生和本科生各级先进的国家研究设施提供研究机会和培训，其中大量包括代表性不足的女学生。

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 (Yeshiva University), 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.