The Evolution of Nanothermoelectricity
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The Evolution of Nanothermoelectricity
Mildred Dresselhaus Department of Physics and Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, U.S.A.
ABSTRACT A personal review is presented. We review the renaissance in thermoelectric materials research that started in 1993 with the introduction of the nanostructure concept as a potential method to both increase the power factor and decrease the thermal conductivity and to even do both at the same time. The earliest work was limited to model systems for the demonstration of proof of principle. More recently the focus has evolved into demonstration of embedding the phenomena into bulk samples based on composites and superlattices. We here review this evolution of the nanothermoelectricity field. The resulting current activity is attracting many new researchers, industrial interest and the emergence of new ideas. We now look to the further development of these new ideas, and to the introduction of more new ideas and new approaches, as the field is now approaching the stage of commercial relevance. INTRODUCTION Thermoelectric materials entered an active growth period in the 1950s when doped semiconducting materials with good thermoelectric properties were produced that could be doped either n-type or p-type [1,2]. By about 1960, thermoelectric materials reaching values of ZT= S2σT/ߢ ~ 1 were achieved. In this early era, Bi2Te3, the main commercial thermoelectric material used until the present time, was developed. We then hit a 30 year period, from 19601990, when the thermoelectrics field saw much less activity. In the early 1990s, the French Navy and the US Navy both developed an interest to develop actual thermoelectric devices for energy utilization aboard submarines. Stimulated by their interest in thermoelectric materials for a specific application area, researchers were encouraged to look for new materials and new concepts to reinvigorate this research field and to stimulate interest in thermoelectricity. At that time, I and my collaborator Professor Jean-Paul Issi at the Catholic University in Louvain la Neuve met in a nice restaurant near his university for discussions with John Stockholm from Paris whom we both knew quite well from French industry. John Stockholm brought with him to dinner a high official from the French Navy. The outcome of these dinner discussions led to two possible new research directions for advancing our knowledge, both involving promising new materials. The first research direction pointed to the examination of the many new materials that were uncovered during the 1960--1990 time frame that might have low thermal conductivity, and Jean-Paul Issi said that he would explore this idea and he took on this
challenge. I took on the exploration of the second research direction of looking into nanoscale materials, which were basically unexplored before 1960, and although not much was known about them in 1990 regarding their possible relevance to thermoelectrics, it was a lot
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