One step synthesis and sintering of Ni and Zn substituted tetrahedrite as thermoelectric material

Tetrahedrite mineral family, one of the most widespread sulfosalts on Earth's crust, seems to meet the right features for an attractive sustainable p-type thermoelectric material, showing relatively high conversion efficiency. The sulphide powders were ball milled and then one-step simultaneous synthesis and sintering process was performed by open die pressing (ODP). This simple, fast, and easy scalable route was extensively discussed for the first time in this work and permitted to obtain thermoelectric pellets starting from sulphide precursors, with a whole process lasting less than 6 h. 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 precursors 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.