FAST AND SCALABLE ROUTE FOR TETRAHEDRITE PELLET PRODUCTION FOR THERMOELECTRIC APPLICATIONS

The interest in thermoelectric materials raised in the recent years due to the possibility to design thermoelectric generators (TEGs), reliable solid-state devices for waste heat recovery valuable in particular contexts where the employment of other technologies results inconvenient. Nowadays, the challenge in the thermoelectric field seems to be the identification of efficient thermoelectric materials which should be also inexpensive, easy to synthesize, and comprised of earth-abundant elements. On this basis, tetrahedrite mineral family (Cu12-xTrxSb4S13 where, for instance, Tr could be Mn, Fe, Co, Ni, or Zn), one of the most widespread sulfosalts on Earth's crust, seems to meet the right features for an attractive sustainable p-Type Pb-free thermoelectric material showing relatively high conversion efficiency [1,2]. The sulphide precursor powders were ball milled and then one-step simultaneous synthesis and sintering process was performed by open die pressing (ODP) [3]. By this simple, fast, and easy scalable route, thermoelectric pellets with a whole process lasting less than 6 hours. Both Zn and Ni cations were added as partial substituents of Cu in Cu12Sb4S13 permitting to considerably improve the thermoelectric performances of the undoped material prepared by ODP. The influence of precursor ratio on the tetrahedrite phase, secondary phase content and stoichiometry were investigated by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The density and mechanical stability of samples were evaluated as a function of the chemical composition and processing parameters. A complete thermoelectric characterization was carried out for samples with different Zn and Ni substitution up to 400 °C.