CAREER: Flexoelectric Effect in Ferroelectric Nanowires for High-Performance Nanogenerators

这项教师早期职业发展(CALEAR)计划奖项的目标是从根本上了解单晶铁电纳米线(NWS)中的挠曲电效应(由非均匀应变引起的极化)。纳米尺度上极大的弯曲电极化增强的理论预测也将得到验证。如果这是真的，它将使高效的纳米发电机成为可能，用于纳米级的机械能量收集。这项研究将主要集中在BaTiO3NWS，因为块体多晶BaTiO3体材料具有最高的挠曲电系数。其他钙钛矿型铁电纳米晶，如PbTiO_3和PZT(PZT)，也将被研究以揭示阳离子对挠曲电性的贡献。大部分研究将利用这些表征良好的纳米粒子作为最先进的扫描探针显微镜研究的基础，这将量化固有的挠曲电系数，测试挠曲电增强的预测，并确定对挠曲电效应的相位和磁区贡献。此外，在实验测量的支持下，还将从理论上预测纳米级的本征挠曲电系数和机电能量转换效率。这项研究将提供对纳米级挠曲电效应的深入、实验基础的理解，有望为指导具有显著提高机电能量转换能力的纳米发电机的设计提供变革性的知识，更广泛地说，将为传统的压电和铁电器件的缩小尺寸和提高性能奠定材料科学基础。该项目将被整合到大学范围内的项目中，以接触高中生和K-12教师，并吸引来自代表不足的少数族裔(URM)的学生进入科学、技术、工程和数学学科。将建立一个长期的循序渐进的教育计划，指导、指导和培训URM学生，从高中生到大学新生，再到高年级本科生。这一努力旨在提高威斯康星大学麦迪逊分校学生的多样性。与校园教师研究体验计划的合作将使我们能够接触到对先进纳米科学和纳米技术感兴趣的高中教师，并帮助他们在自己的学校创建或改进科学课程。一套综合的纳米技术教育讲稿将根据该协会的新纳米技术课程编制并在网上分发。

The objective of this Faculty Early Career Development (CAREER) Program award is to gain fundamental understanding of the flexoelectric effect (polarization induced by inhomogeneous strain) in single-crystalline ferroelectric nanowires (NWs). The theoretical prediction of a gigantic flexoelectric enhancement of the polarization on the nanometer scale will also be tested. If true, it would make possible highly efficient nanogenerators for nanoscale mechanical energy harvesting. The research will focus mainly on BaTiO3 NWs because bulk polycrystalline BaTiO3 has the highest reported flexoelectric coefficient. Other perovskite ferroelectric NWs, such as PbTiO3 and Pb(ZrxTi1-x)O3 (PZT), will also be studied to reveal the cation contribution to flexoelectricity. The bulk of the research is to use these well-characterized NWs as a basis for state-of-the-art scanning probe microscopy studies, which will quantify the intrinsic flexoelectric coefficients and testing the prediction of flexoelectric enhancement and establish the phase and domain contributions to the flexoelectric effect. In addition, supported by experimental measurements, the nanoscale intrinsic flexoelectric coefficients and the mechanical-to-electric energy conversion efficiencies will be theoretically predicted.This research will provide an in-depth, experimentally grounded understanding of the flexoelectric effect at the nanometer scale, which is expected to generate transformative knowledge for directing the design of nanogenerators with dramatically improved mechanical-to-electric energy conversion capability and, more generally, will establish a materials science basis for reduction in size and enhancement in performance of conventional piezoelectric and ferroelectric devices. This project will be integrated into university-wide programs to reach out to high-school students and K-12 teachers and attract students from underrepresented minorities (URM) to science, technology, engineering, and mathematics disciplines. A long-term stepwise education program will be established for instructing, mentoring, and training URM students from high school students, to college freshmen, to senior undergraduate students. This effort aims at improving the diversity of students at UW-Madison. Collaboration with the campus Research Experience for Teachers program will allow us to outreach to high school teachers who are interested in advanced nanoscience and nanotechnology and to help them create or improve science courses in their own schools. A set of comprehensive lecture notes for nanotechnology education based on the PI's new nanotechnology course will be developed and distributed online.