Materials World Network: Experimental Observation and Theoretical Modeling of Domain Evolution in Ferroelectrics

该奖项由2009年美国复苏和再投资法案(公法111-5)资助。铁电陶瓷具有独特的性能，包括压电性、热释电性、电光效应、相变和偏振开关。这些特殊的性质使它们在广泛的技术应用中发挥了作用。例如，医用超声波扫描仪、随机存取存储器、红外摄像机传感器、电光调制器、声纳信标、振动控制器和柴油发动机喷油器都使用铁电材料。提出的研究计划将推动铁电材料行为的实验和理论表征领域的发展。该程序开发的实验和理论方法将适用于其他“智能”材料的研究，包括形状记忆合金和铁磁形状记忆合金。通过这项研究，博士生将在一个与国际活动合作的项目中接受培训：学生将在德克萨斯大学奥斯汀分校和牛津大学(英国)接受培训。为了扩大任职人数不足群体的参与，主要调查员将继续利用机构资源招聘妇女和少数族裔学生的记录。这项研究最终将通过发展对铁电材料行为的基本了解来造福社会，这将支持和刺激用于众多和不同技术应用的新型铁电器件的设计。该材料世界网络国际合作研究计划的优点来自于单晶铁电陶瓷中铁电畴结构成核、生长和演化的最新实验表征(英国)和理论建模(美国)的联合应用。到目前为止，已经有几个关于铁电晶体的杰出的实验和理论研究，但这些研究都没有系统地将实验观察与建模框架相结合，这些实验观察可以批判性地检验模型预测，而建模框架反过来又能够建议创新的实验研究。该研究的实验部分使用原子和压电力显微镜、X射线同步加速器和双折射方法来直接观察在热、电和机械载荷下的铁电磁畴结构的演变。每种实验构型也通过Landau-Ginsburg-Devonshire相场方程的详细数值解的透镜被研究和解释。这些研究主要集中在两个方面：(1)在静电场和交变磁场作用下包括孤立磁区在内的现有结构的演化，以及磁区针和磁区涡旋的演化，以及(2)由于居里温度的冷却以及电极头和材料夹杂物等场集中器的成核。在研究过程中，两名博士生将在一个与国际活动密切合作的项目中接受培训。每个学生将在对应的机构呆六个月，这些交流的时间安排是为了让研究型学生一起工作，从而获得理论和实验方法方面的专业知识。本研究对磁畴结构演化的详细实验表征和预测建模将为下一代新型铁电器件的设计提供支持和激励。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Ferroelectric ceramics have unique properties, including piezoelectricity, pyroelectricity, the electro-optic effect, phase change, and polarization switching. These special properties make them useful for a wide range of technological applications. For example, medical ultrasound scanners, random access memories, infrared camera sensors, electro-optic modulators, sonar beacons, vibration controllers, and diesel engine fuel injectors all make use of ferroelectric materials. The proposed research program will advance the field of experimental and theoretical characterization of the behavior of ferroelectric materials. Experimental and theoretical methods developed in this program will be applicable to the study of other "smart" materials including shape memory alloys and ferromagnetic shape memory alloys. Through this research, doctoral students will be trained in a collaborative project with international activity: students will train at University of Texas, Austin, and University of Oxford (UK). To broaden participation from underrepresented groups the principal investigators will continue their track record of leveraging institutional resources to recruit women and minority students. The research will ultimately benefit society by developing a fundamental understanding of the behavior ferroelectric materials, which will support and stimulate the design of novel ferroelectric devices for numerous and diverse technological applications.The merit of this Materials World Network international collaborative research program originates from the joint application of state of the art experimental characterization (in the UK) and theoretical modeling (in the US) of domain structure nucleation, growth and evolution in single crystal ferroelectric ceramics. To date there have been several outstanding experimental and theoretical studies on ferroelectric crystals, but none of these studies has systematically integrated experimental observations that can critically test model predictions with a modeling framework that is, in turn, able to suggest innovative experimental studies. The experimental component of the research uses atomic and piezo-force microscopy, X-ray sychrotron, and birefringence methods to directly observe ferroelectric domain structure evolution under thermal, electrical and mechanical loadings. Each experimental configuration is also studied and interpreted through the lens of detailed numerical solutions of the Landau-Ginsburg-Devonshire phase-field equations. The studies focus on two categories: (1) evolution of existing structures including isolated domain walls subjected to static and alternating fields, and the evolution of domain needles and domain vortices, and (2) the nucleation of domain structures due to cooling through the Curie temperature, and from field concentrators like electrode tips and material inclusions. During the course of the research, two doctoral students will be trained in a strongly collaborative project with international activity. Each student will spend six months in the counterpart institution, with these exchanges timed to allow the research students to work together and thus gain expertise in both theoretical and experimental methods. The detailed experimental characterization and predictive modeling of domain structure evolution from this research will support and stimulate the design of the next generation of novel ferroelectric devices.