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

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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.