CAREER: The Evolution of Polar Nanoregions and Its Coupling with Cation-Ordered Domains in Pb(B'B'')O3 Relaxor Ferroelectrics

这项职业计划致力于研究复合钙钛矿型Pb(B‘B“)O_3弛豫铁电体中的极性纳米区域与阳离子有序结构域之间的相互作用，以及化学结构域对极化结构域动态转变的影响。这两种类型的结构域都是纳米级的，它们的相互作用是观察到的优异性能的物理来源。外加电场导致了极区向铁电宏区的转变，对应于一级相变。然而，我们目前对这两个纳米尺度特征之间的耦合的了解非常有限，并且从来没有探索过在外场存在的情况下极性纳米结构域的演化。在这项研究中，将采用一种独特的原位透射电子显微镜方法，以便在受控低温下将电压传递到透射电子显微镜样品。这项实验旨在实时可视化弛豫陶瓷中基本纳米级特征的演变。这个项目的结果意义重大，因为它们有望(I)确定化学有序和电偶极子有序之间的耦合，(Ii)建立场诱导相变的机制，以及(Iii)改进现有的动力学模型，以更好地理解弛豫行为。研究结果将在纳米材料科学的更广泛背景下处理，并用于纳米科学教育。将开展综合教育活动，通过让不同层次的大量学生接触这一新知识来促进纳米科学教育。通过为爱荷华州高中科学教师举办的一系列暑期讲习班，以及由高中实习生为5-8年级学生创建的基于网络的教学计划，纳米材料的科学和应用将被引入K-12课程。作为一个代表性不足的群体，女性将通过爱荷华州立大学的女性科学与工程项目(PWSE)和工程学院的互联网探索者项目参与进来。

This CAREER project addresses the interactions between the polar nanoregions and the cation ordering domains and the effects of the chemical domains on the dynamic transition of the polar domains in relaxor ferroelectrics of complex perovskite Pb(B'B")O3. These two types domains are both on the nanometer scale and their interplay is the physical origin for the observed superior properties. Application of an electric field leads to a transformation of the polar regions into ferroelectric macrodomains, corresponding to a first order phase transition. However, our current understanding of the coupling between these two nanoscale features is very limited and the evolution of the polar nanodomains in the presence of external fields has never been explored. A unique in situ transmission electron microscopy (TEM) approach will be taken in this study in order to deliver electric voltage to TEM specimens at controlled low temperatures. This experiment seeks to visualize, in real time, the evolution of fundamental nanoscale features in relaxor ceramics. The results derived from this project are significant because they are expected to (i) identify the coupling between chemical order and electric dipole order, (ii) establish the mechanism of the field-induced phase transition, and (iii) refine existing kinetics models for better understanding of relaxor behavior.The research findings will be treated within the broader context of nanomaterials science and utilized for nanoscience education. Integrated educational activities will be pursued to promote nanoscience education by exposing a large number of students at various levels to this new knowledge. The science and application of nanomaterials will be introduced into the K-12 curriculum through a series of summer workshops for Iowa high school science teachers and Web-based lesson plans for 5th-8th graders created by high school interns. As an underrepresented group, women will be involved through the Iowa State University's Program for Women in Science and Engineering (PWSE) and the Internet Explorers program of the College of Engineering.