GOALI Collaborative Research: Intrinsically Minimal Thermal Conductivity in I-V-VI2 Thermoelectric Semiconductors

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

CBET-0754023 Heremans The goal of this work is to lay the scientific groundwork to develop a new class of thermoelectric semiconductors based on I-V-VI2 compounds. This class of compounds possesses intrinsically the lowest lattice thermal conductivity possible in a crystalline material. Low lattice thermal conductivity is one of the prime factors in producing a high thermoelectric figure of merit; and ii) the PIs of this proposal have devised a method for preparing AgSbTe2 with very low carrier concentrations and high mobilities. The program is a GOALI with BSST as an industrial partner. Partnership with BSST, the world's largest user of thermoelectric materials, will ensure a rapid evaluation of the commercial potential of any new material produced. Intellectual Merit This research will focus on rigorous experimental studies of the lattice and electronic properties of this class of semiconductors. The lattice thermal conductivity will be measured from 4 K to the melting point, with the Ag/Sb ordering as independent parameter. The data will be interpreted in terms of Umklapp and Normal phonon scattering processes, which will be derived without using adjustable relaxation times, and of the bond anharmonicity. Detailed band structure and Fermi surface information will be gleaned from Shubnikov-deHaas measurements. Preliminary first principle calculations show that AgSbTe2 may actually be a semimetal, and that its exact band structure is a function again of the amount of Ag/Sb ordering. The full galvanomagnetic, thermoelectric and thermomagnetic properties will be measured up to the melting point, and used to determine mobilities and electron scattering mechanisms. Broad Impact Enhanced thermoelectric materials will enable an inexpensive method for converting solar thermal energy into electricity, and also will make possible the conversion of a fraction of the heat wasted by conventional heat engines, such as automotive power plants, into usable power. This is thus potentially transformative research that promises to reduce our reliance on fossil fuels, and to have a significant positive impact not only on the science and technology community, but on society in general. The partnership with BSST will ensure that the new thermoelectric materials are rapidly available for evaluation of their commercial potential. BSST will feed important information back to the research team about engineering criteria and the actual performance of the new materials in real electrical power generators. In the realm of education, this project will provide training for graduate students in a broad array of materials synthesis and characterization techniques. Additionally, results of the research will be incorporated into classes being developed by the PI?s in the areas of thermal transport and thermoelectricity. The significance of the broader issue of energy efficiency and usage that this research addresses will be integrated into the well established outreach programs at both institutions. Finally, the involvement of an industrial partner will give the students real-world experience into the engineering of transformative technological products and insight into the world of the energy industry. This project is jointly funded by the Thermal Transport Processes (TTP) Program, of the Chemical, Bioengineering, Environmental, and Transport Systems (CBET) Division, and by the Grant Opportunities for Academic Liaison with Industry (GOALI) Program, of the Industrial Innovation & Partnerships (IIP) Division, all within the Directorate for Engineering (ENG).