Thermoelectric materials are capable of capturing waste heat and converting it into usable energy. Tetrahedrite (Cu12Sb4S13) is an earth-abundant compound that has been widely investigated as a thermoelectric with its inherently low thermal conductivity in part due to its complex unit cell structure. Utilizing a solution-phase modified polyol process, we have synthesized phase-pure, surfactant- and ligand-free tetrahedrite on the gram scale. This produces nanostructured material that successfully further reduces the thermal conductivity relative to tetrahedrite produced by more time and energy intensive conventional solid-state methods. Relevant to tune the concentration of charge carriers to improve performance, we have recently shown the compatibility of our synthetic approach with the incorporation of a wide-range of dopants on the Cu, Sb, and S sites. This is the first solution-phase method to produce six of these compounds. The bottom-up synthesis by the polyol method was investigated as a function of temperature and time to determine the reaction growth mechanism and observe the evolution of the different chemical phases. Key intermediates for the formation were digenite (Cu1.8S), covellite (CuS), and famatinite (Cu3SbS4). All synthetic products are characterized by powder x-ray diffration and scanning electron microscopy with energy dispersive x-ray spectroscopy. For thermoelectric applications, it is imperative that thermal stability be evaluated. We find that the nanostructured undoped tetrahedrite has reduced thermal stability relative to samples made by solid-state methods, while first-row transition metal dopants on the Cu site increase the stability of material. Toward the application of this material produced by our low-energy chemical method, this research determined the growth mechanism, demonstrated synthetic versatility to tune material composition, and investigated physical properties impacted by nanostructuring and doping.

Tetrahedrite nanomaterials for thermoelectrics: Synthetic versatility, reaction pathway, and thermal stability

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.