Tetrahedrite Sintering Conditions: The Cu11Mn1Sb4S13 Case

Manganese-doped tetrahedrites, with Cu 11 Mn 1 Sb 4 S 13 composition and synthesized by the solid-state method, were hot-pressed at temperatures ranging between 788 K and 848 K. The structure, microstructure, phase purity and thermoelectric properties of the materials were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and density studies. According to the XRD analysis, all the hot-pressed materials presented a main tetrahedrite phase. However, very small amounts of chalcostibite (CuSbS 2 ) were detected by SEM–EDS. While keeping the pressure constant at 60 MPa, an increase in density with hot-pressing temperature was observed, reaching a maximum relative density of 97% for the samples hot-pressed at 848 K. Measurements of the electrical transport properties indicated higher thermal conductivity, electrical conductivity and Seebeck coefficient for the denser samples, with a greater power factor leading to an increase of > 10% in the figure of merit ( zT ) relative to the less dense materials.