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

这个CAREER项目解决了极性纳米区域和阳离子有序域之间的相互作用，以及化学域对复杂钙钛矿Pb（B 'B”）O3弛豫铁电体中极性域动态转变的影响。这两种类型的域都是在纳米尺度上，它们的相互作用是所观察到的优越的上级性能的物理起源。施加电场导致极性区域转变成铁电宏畴，对应于一阶相变。然而，我们目前对这两个纳米尺度特征之间的耦合的理解是非常有限的，并且在外场存在下极性纳米畴的演化从未被探索过。一个独特的原位透射电子显微镜（TEM）的方法将在这项研究中，以提供电压TEM标本在受控的低温。这个实验试图可视化，在真实的时间，在弛豫陶瓷的基本纳米尺度特征的演变。该项目的研究结果具有重要意义，因为它们有望（i）识别化学有序和电偶极有序之间的耦合，（ii）建立场诱导相变的机制，（iii）完善现有的动力学模型，以更好地理解弛豫行为。研究结果将在更广泛的纳米材料科学背景下进行处理，并用于纳米科学教育。我们会继续推行综合教育活动，让不同程度的学生接触这方面的新知识，以促进纳米科学教育。纳米材料的科学和应用将通过为爱荷华州高中科学教师举办的一系列暑期讲习班和由高中实习生为5 - 8年级学生制作的基于网络的课程计划，引入K-12课程。作为一个代表性不足的群体，妇女将通过爱荷华州州立大学的科学和工程妇女方案以及工程学院的互联网探索者方案参与。

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.