Simultaneous synthesis and sintering of tetrahedrite based thermoelectric materials

Nowadays, the real challenge in the thermoelectric field seems to be the identification of efficient thermoelectric materials which should be inexpensive, easy to synthesize, and comprised of Earth-abundant elements. On this basis, tetrahedrite mineral family (Cu12-xTrxSb4S13 where Tr= Cu, Mn, Fe, Co, Ni, Zn), one of the most widespread sulfosalts on Earth's crust, seems to meet the right features for an attractive p-Type Pb-free thermoelectric material, showing a relatively high conversion efficiency [1, 2]. Working on the synthetic geomimetic tetrahedrites is useful to improve the knowledge about this peculiar material, leading to understand how enhance it and how to exploit the natural tetrahedrite mineral more effectively. In this work, both Zn and Ni cations were employed as substituents, according to the stoichiometry Cu10Zn2-xNixSb4S13, by means of ball milling treatment of sulphide precursor powders and one step simultaneous synthesis and sintering by Open Die Pressing [3]. This process is a scalable simple and fast route that lasted few hours, a very short time if compared with those reported in literature so far. The influence of the stoichiometry, the synthesis conditions and the reactive consolidation process parameters on the tetrahedrite phase content and density of the samples were investigated by X-ray diffraction (with a profile Rietveld refinements) and scanning electron microscope (equipped with energy dispersive X-ray spectroscopy). Furthermore, the thermoelectric functional properties of the samples were investigated by electrical conductivity and Seebeck oefficient measurements and Laser Flash Analysis for the thermal conductivity.