Non-Stoichiometric Ferroelectrics and their Associated Thermoelectric Properties

非技术性：该项目的研究为可持续高性能热电器件开辟了新的研究策略，可能对节能，减少二氧化碳和环境产生重大社会影响。本研究探讨了两种不寻常的功能材料：铁电体和热电体之间的接口，以实现低成本和高效率的能量收集。用于发电机的低成本热电材料解决方案具有重大的经济优势;例如，每辆汽车，家用炉和工厂排气烟囱都可以配备配备热电设备和这些新的热电材料和策略的热交换器。有一个重要的教育推广活动与当地学校（公园森林和尼塔尼山中学），从事材料科学6-8年级的学生。在这个项目下，正在设计一个材料分类练习，以测试儿童以前通过“展示和触摸”选择金属和绝缘体的看法和偏见。同样的材料也被引入到宾夕法尼亚州立大学的入门材料课程中，以了解这些学生的观点与年幼学生的观点有何不同。这一概念的理论基础支撑了将铁电材料转化为热电材料的技术进步。根据初步数据，宾夕法尼亚州立大学在铁电-热电领域的核心知识产权已经得到保护。在整个项目中，活动范围从当地教育到全球能源-环境-经济效益。技术：这项研究探讨了两种不寻常的功能材料之间的界面：铁电体和热电体。这项工作的目的是提供一个更广泛的理解高度非化学计量的铁电材料附近的临界电子载流子浓度分离半导体和金属导电，所谓的莫特标准。对非化学计量钙钛矿BaTiO 3-d和001钨青铜（Sr，Ba）Nb 2 O 6-d铁电材料的热电性能的初步观察显示出有吸引力的特性，该项目将建立：（1）各种铁电组合物和结构的一般结构-热电性质数据，（2）电导率、塞贝克系数和热导率的量化和建模，识别控制输运的材料物理，（3）对“最佳”铁电-热电的洞察，（4）不同材料中铁电相变行为的本质与超导-金属相变之间的关系，以及（5）光学带边行为的分析，量化声子。电子耦合，和结构的高度非化学计量的铁电体跨越相变的修改。在这个项目下产生的非化学计量的铁电体的四赫兹光谱测量被用来建立在过渡区的声子动力学的详细理解，并可以通过挑战铁电材料在这些独特的条件下的相变的理解开辟一个新的子领域。与捷克物理研究所的研究合作将使参与这项调查的宾夕法尼亚州立大学学生认识到全球科学网络的重要性，以及与拥有独特和世界一流设施和专业知识的团体合作的重要性。

NON-TECHNICAL: The research in this project opens up new research strategies for sustainable high performance thermoelectrics that could have major societal impacts on energy savings, CO2 reduction and the environment. This investigation explores the interface between two unusual classes of functional materials: ferroelectrics and thermoelectrics, for low cost ¡V high efficiency energy harvesting. There are major economic advantages with a lower cost thermoelectric materials solution for generators; as an example, every automobile, household furnace, and factory exhaust chimney could have heat exchangers equipped with thermoelectric devices and these new enabling thermoelectric materials and strategies. There is an important educational outreach activity with local schools (Park Forest and Mount Nittany Middle Schools), engaging students in grades 6-8 in material science. Under this project, a materials classification exercise is being designed to test previous perceptions and prejudices of the children towards selecting metals and insulators through ¡§show and touch. The same materials are being introduced to introductory materials classes at Penn State University to see how opinions differ from those of the younger children. The theoretical basis of this concept underpins the technical part of the advances used in transforming ferroelectric materials to thermoelectrics. Based on preliminary data, the core intellectual property for Penn State University in the ferroelectric-thermoelectrics area has already been protected. Across this project, activities range from local education to global energy-environment-economic benefits in terms of its impact. TECHNICAL: This investigation explores the interface between two unusual classes of functional materials: ferroelectrics and thermoelectrics. The aim of this work is to provide a broader understanding of highly non-stoichiometric ferroelectric materials near the critical electronic carrier concentration separating semiconducting and metallic conduction, the so-called Mott criterion. Initial observations of thermoelectric properties in non-stoichiometric perovskite BaTiO3-d and 001 tungsten bronze (Sr,Ba)Nb2O6-d ferroelectric materials shows attractive properties, and this project will establish: (1) general structure-thermoelectric property data for various ferroelectric compositions and structures, (2) quantification and modeling of electrical conductivity, Seebeck coefficient, and thermal conductivity, identifying the materials physics controlling the transport, (3) insights into the "best" ferroelectric-thermoelectrics, (4) the relation between the nature of the ferroelectric phase transition behavior and the semiconductor-metallic transition in different materials, and (5) analysis of the optical band edge behavior, quantifying phonon¡Velectron coupling, and structural modifications in the highly non-stoichiometric ferroelectrics across phase transitions. Tetrahertz spectroscopy measurements of the non-stoichiometric ferroelectrics produced under this project are used to establish detailed understanding of the phonon dynamics in the transition region and could open up a new sub-field by challenging the understanding of phase transitions in ferroelectric materials under these unique conditions. The research collaboration with the Czech Institute of Physics will expose the Penn State University students involved in this investigation to the importance of the global network of science and collaboration with groups with unique and world-class facilities and expertise.