Understanding thermal and electronic transport in high-performance thermoelectric skutterudites

Abstract

Filled Sb-based skutterudites are considered one of the most appealing thermoelectric materials in the mid temperature range. Even though Sb is not one of the most abundant elements in nature, the large thermoelectric figure of merit of these materials makes them attractive for applications such as thermoelectric generators. In order to get deeper insight into the fundamental physical mechanisms of thermal and electronic transport properties, we studied the temperature dependent electrical resistivity, Seebeck coefficient, thermal conductivity and specific heat. Three groups of skutterudites with excellent thermoelectric performance were investigated: (a) DDyFe4-xCoxSb12 (0 ≤ x ≤ 4; 0.08≤ y ≤ 0.7), to study the influence of Fe/Co substitution and the resulting filling level y as well as the influence of grain size, (b) DD0.7Fe3CoSb12 samples prepared from the same powder to study the effect of different synthesis nanostructuring techniques (hot-pressed, hot pressed and processed via high pressure torsion and cold-pressed and processed via high pressure torsion) and (c), a DD-filled skutterudite with and without Sb/Sn substitution before and after annealing. An overview of experimental investigations of the low-temperature transport is given and appropriate phenomenological models are adopted to elucidate the temperature-dependent features and the origin of high thermoelectric performance in these systems.