CAREER: Enhanced Pyroelectric and Electrocaloric Effects in Complex Oxide Thin Film Heterostructures

非技术描述：功能复合氧化物材料开发的进步使许多日常使用的设备成为可能，从存储器到执行器，甚至更多。该项目正在加深对材料电热响应的了解，并找到增强这些效应的方法，以实现先进的热成像(例如夜视系统)、废热能量转换以提高能效、用于高科技应用的新型电子发射以及用于纳米电子设备的低功率固态冷却。该项目正在开发一种设计算法，通过该算法，研究人员可以增强材料在此类应用中的电场和温度依赖响应。可能的应用范围从通信到数据存储，从逻辑到传感设备。这些领域的基础研究促进了美国在日益增长的绿色经济和高科技领域的创新。该项目包括研究创造新的和复杂的材料，材料设计和优化的计算和理论方法，以及材料性能的高级表征。该项目还通过向学生介绍先进的功能材料，并扩大未被充分代表的学生群体在科学和工程职业中的参与(通过个人互动和招募)，促进在K-12/本科/研究生教育水平上的发现和理解。技术细节：该项目提供了所谓的磁电热效应和热电磁效应的首批研究之一，该效应利用多铁性/磁电学中的耦合序参数。此外，该项目正在研究受挫的铁电有序，这应该会随着外加磁场的变化而产生较大的熵变化。该研究项目结合了唯象模型、尖端薄膜生长技术(包括脉冲激光沉积和分子束外延)和现代表征技术的进展，以加深对复杂氧化物材料热电响应(即热释电和电热效应)的物理和热力学的理解。该项目正在为这种热电反应的潜在机制提供新的见解，并寻求操纵和控制铁氧化物中熵变化的温度和场依赖关系的途径。该项目的总体目标是加深对这些效应的基本了解，开发对薄膜系统响应的预测能力，并探索这些材料的性质和最终性能，以使它们能够在设备中使用。作为该项目的一部分，研究人员正在创造和表征复合氧化物材料的高质量、异质外延、薄膜异质结构和纳米结构，并反过来正在研究通过探索现代材料中熵的温度和场依赖性来增强材料热电响应的创新方法。该项目还通过开发这些热力学性质的新型Ginzburg-Landau-Devonshire模型来提供对这些效应的基本物理见解，该模型包括来自磁区壁、多磁区结构、层状异质结构、应变和成分梯度以及薄膜中常见的其他特征的影响。最后，该项目试图找出并克服在表征这种性质方面的不足，包括利用新技术首次直接测量薄膜中的这种效应。

NON-TECHNICAL DESCRIPTION: Advances in the development of functional complex oxide materials have enabled many of the devices that are utilized on a daily basis from memories to actuators and beyond. This project is developing a deeper understanding of electro-thermal responses of materials and finding routes to enhance those effects to enable advanced thermal imaging (e.g., night-vision systems), waste-heat energy conversion for energy efficiency, novel electron emission for high-tech applications, and low-power solid-state cooling for nanoelectronics. This project is developing a design algorithm by which researchers can enhance the electric-field and temperature-dependent response of materials for such applications. Possible applications range from communications to data storage to logic to sensing devices. Fundamental research in these fields fosters the United States innovation in the growing green economy and high-technology spaces. The project includes research on the creation of new and complex materials, computational and theoretical approaches to materials design and optimization, and advanced characterization of materials properties. The project also promotes discovery and understanding at the K-12/undergraduate/graduate education levels by introducing students to advanced functional materials and broadening the participation (through personal interaction and recruitment) of underrepresented student groups in science and engineering careers.TECHNICAL DETAILS: This project provides the one of the first studies of so-called magneto-electro-caloric and pyro-electric-magnetic effects, which make use of coupled order parameters in multiferroic/magneto-electrics. Additionally, the project is investigating frustrated ferroelectric order which should provide for large entropic changes with applied fields. The research project combines advances in phenomenological models, cutting-edge thin-film growth techniques (including pulsed-laser deposition and molecular beam epitaxy), and modern characterization techniques to develop a deeper understanding of the physics and thermodynamics of thermo-electrical responses (i.e., pyroelectric and electrocaloric effects) in complex oxide materials. This project is providing new insight into the underlying mechanisms of such thermo-electrical responses and seeking pathways to manipulate and control the temperature- and field-dependence of entropic changes in ferroic oxides. The overall goal of the project is to further the fundamental understanding of these effects, to develop predictive capabilities for responses in thin-film systems, and to probe the properties and ultimate performance of these materials to enable their use in devices. As part of this project, the researchers are creating and characterizing high-quality, heteroepitaxial, thin-film heterostructures and nanostructures of complex oxide materials and in turn, are investigating innovative approaches to enhance thermo-electrical responses in materials by exploring the temperature- and field-dependence of entropy in modern materials. The project is also providing fundamental insight into the physics of these effects by developing novel Ginzburg-Landau-Devonshire models of these thermodynamic properties that include effects from domain walls, polydomain structures, layered heterostructures, strain and composition gradients, and other features common in films. Finally, the project seeks to identify and overcome inadequacies in characterization of such properties, including the utilization of new techniques to provide the first direct measurement of such effects in thin films.