However, the current efficiency of thermoelectric conversion is insufficient for commercially viable coolers and generators on a larger scale. Prospective applications are multifarious, ranging from radiation and temperature sensors, vacuum gauges, to Peltier coolers and power generators. Thermoelectricity is the striking ability of some materials to generate an electrical voltage when subjected to a temperature gradient (and vice versa).
Further, we explore new avenues in which electronic correlations may contribute to the improvement of thermoelectric performance. Focussing on intermetallics such as silicides, antimonides, skutterudites, and Heusler compounds we showcase successes and challenges for the realistic simulation of transport properties in the presence of electronic correlations. From the latter, FeSi emerges as an orbital-selective Kondo insulator. We show a retrospective of the understanding of these phenomena, discuss the relation to heavy-fermion Kondo insulators-such as Ce 3Bi 4Pt 3 for which we present new results-and propose a general classification of paramagnetic insulators. This insulator-to-metal crossover is accompanied by spectral weight-transfers over large energies in the optical conductivity and by a gradual transition from activated to Curie–Weiss-like behaviour in the magnetic susceptibility. Members of this class-such as FeSi and FeSb 2-display an unusual temperature dependence in various observables: insulating with large thermopowers at low temperatures, they turn bad metals at temperatures much smaller than the size of their gaps. We review many-body effects, their microscopic origin, as well as their impact on thermoelectricity in correlated narrow-gap semiconductors.
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