Domain Boundary - Grain Boundary Interactions in Ferroelectrics

非技术描述：铁电材料（具有自发极化，可以通过外加电场重新定向-铁磁材料的电模拟）包含数十亿美元的产业；在几乎所有情况下，功能性质都取决于畴壁（具有不同极化方向的区域之间的边界）的迁移率。该项目量化了现实微观结构对这些畴壁迁移率的作用，并将这些结果广泛传播给科学界和工业界。在研究生阶段，该项目正在培养将成为下一代科技领袖的学生。毕业生通常会在高科技公司或大学教职员工中找到工作。此外，首席研究员将完成教材的第二版，材料工程：粘合，结构和结构-性能关系。技术细节：铁电材料中与钉住畴壁和相边界运动相关的基本过程和长度尺度目前对一般情况知之甚少。本项目采用电学和机电特性、透射x射线显微镜、纳米探针x射线散射和压电响应力显微镜相结合的方法，建立了一个定量数据库，研究不同的机械边界条件，包括薄膜应力、晶界取向角和相互作用的晶体学缺陷对畴壁相关运动的影响。来自宾夕法尼亚州立大学、阿贡国家实验室和丹麦技术大学的跨学科研究小组正在制备和表征具有广泛不同晶界角的模型样品，以便直接测量Pb(Zr,Ti)O3薄膜中畴壁相关运动的长度尺度。功能属性是通过Rayleigh和Preisach方法的结合来映射的。通过压响应力显微镜进行的大面积测量与局部测量相辅相成，以绘制不同应变状态和晶界取向偏差下畴壁集体运动的簇的大小。在场激发下用纳米探针衍射测量对样品进行了询问。此外，在确定为强或弱响应的区域中，局部结构域结构正在通过x射线暗场显微镜进行研究，以便在空间上绘制缺陷/结构域壁相互作用。定位主要钉钉位点的能力，然后在电刺激样品的同时对这些区域进行结构上的非破坏性探测，使得阐明局部扰动对功能畴壁集体运动的影响成为可能。这些结果使铁电薄膜、陶瓷和单晶的模型得以发展，以更准确地捕捉基本的材料物理。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 DESCRIPTION: Ferroelectric materials (which have a spontaneous polarization which can be reoriented by an applied electric field – the electrical analog of ferromagnetic materials) comprise a multi-billion-dollar industry; in nearly every case, the functional properties depend on the mobility of domain walls (the boundaries between regions with different polarization directions). This project is quantifying the role of realistic microstructure on the mobility of these domain walls, and broadly disseminating these results to the scientific community and industry. At the graduate level, the project is training students who will become next-generation scientific and technology leaders. Graduates typically find employment either at high-tech companies or as university faculty members. In addition, the principal investigator will complete a second edition of the textbook, Materials Engineering: Bonding, Structure, and Structure-Property Relationships.TECHNICAL DETAILS: The fundamental processes and length scales associated with pinning domain wall and phase boundary motion in ferroelectric materials are at present poorly understood for general cases. This project is using a combination of electrical and electromechanical characterization, transmission X-ray microscopy, nanoprobe X-ray scattering, and piezoresponse force microscopy to develop a quantitative database on the way that different mechanical boundary conditions, including film stress, grain boundary misorientation angle, and interacting crystallographic defects influence correlated motion of domain walls. The interdisciplinary team of researchers from Penn State, Argonne National Laboratories and the Technical University of Denmark are preparing and characterizing model samples with a wide range of different grain boundary angles in order to directly measure the length scales over which correlated motion of domain walls occurs in Pb(Zr,Ti)O3 thin films. The functional properties are being mapped through a combination of Rayleigh and Preisach approaches. Large area measurements are being complemented with local measurements via piezoresponse force microscopy to map the size of the clusters where there is collective motion of domain walls for different strain states and grain boundary misorientations. Samples are being interrogated with nanoprobe diffraction measurements under field excitation. Moreover, the local domain structure in regions identified as strongly or weakly responsive are being interrogated via X-ray dark field microscopy in order to spatially map the defect/domain wall interactions. The ability to localize the major pinning sites and then structurally probe those regions non-destructively while exciting the sample electrically allows the possibility of elucidating the impact of local perturbations on the collective motion of functional domain walls. These results are allowing models of ferroelectric films, ceramics, and single crystals to be developed to capture the fundamental material physics more accurately.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.