Enhancement of thermoelectric performance by synergistic effects from multiple dopings in complex oxides

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0854467YuThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The research and education plan centers on understanding and manipulating energy transport phenomena within nanostructured complex oxide materials, as well as educating a broad spectrum of students including graduate, undergraduate, and K-12 students in aspects of energy conversion processes. The research includes investigation of: (1) energy transport phenomena through confined oxide structures; (2) thermal transport in oxygen-deficient, impurity-doped nanostructured oxide materials; and (3) influence of multiple dopants on electron and phonon transport for thermoelectric applications. In addition, the proposed education and outreach program will: (5) educate graduate and undergraduate students, as well as K-12 students and teachers in nano- and micro-scale thermophysical phenomena for energy conversion; and (6) recruit minorities and women to study engineering disciplines and enroll in graduate schools.Intellectual Merit: Significant improvement in conversion of waste heat to electricity using thermoelectric devices hinges upon the simultaneous reduction of thermal conductivity and enhancement of electric conductivity of thermoelectric materials. Recently, several researchers have suggested that the suppression of phonon thermal conductivity is very effective in improving the performance of thermoelectric materials, as this influences thermal transport but often has a minimal influence on electronic transport properties. However, current efforts using state-of-the-art bismuth telluride alloys do not provide sufficient room to obtain a large reduction in thermal conductivity due to the intrinsically low thermal conductivity of these materials. In this regard, it is timely and important to explore materials that have not been considered extensively in the past, such as complex oxides. The electrical and thermal transport properties of these oxides can be altered using various methods, which provides an opportunity to develop new, high-performance thermoelectric materials. For example, the simultaneous use of property tuning methods might produce synergistic effects that will dramatically increase thermoelectric performance. The knowledge gained from this research will advance the fundamental understanding of energy carrier transport through confined structures and will provide a methodology to tailor the properties of many different materials. The understanding of energy-carrier transport will be obtained through a series of experiments and theoretical /computational calculations, that can be used as a platform to identify other promising complex oxides for thermoelectric applications. Broader Impacts: Highly efficient thermoelectric materials have the potential to generate large amounts of electric power from waste heat, while simultaneously reducing greenhouse gas emissions. The research will be integrated into a graduate course as well as core undergraduate courses, and will form the basis for presentations in nanoscience-related courses and seminars, as well as for outreach to K-12 students and teachers through various education programs including the Enrichment Experiences in Engineering (E3) program at Texas A&M University. Visits to minority and K-12 schools in Texas will encourage women and underrepresented groups to pursue undergraduate and graduate studies in various engineering disciplines.