The influence of preparation conditions on the electrical transport properties of tetrahedrites. (2019) - Domingos, Gonçalo
Abstract: Materials with Cu12-x Nix Sb4-y Biy S13-z Sez (0 ≤ x ≤ 1, 0 ≤ y ≤ 0.4, 0 ≤ z ≤ 3) compositions were prepared by melting the elements under vacuum. All samples were studied in the as-cast form, and parts of them were characterized after either a spark plasma sintering or a melt spinning/glass-crystallization procedure. Powder X-ray diffraction shows that all materials are mainly constituted by tetrahedrite, except in the case of the Cu12 Sb4 S10 Se3 composition treated by SPS that is constituted by skinnerite, famatinite and tetrahedrite. Electrical conductivity and Seebeck coefficient measurements point to a large effect of the preparation technique and experimental conditions on the electrical transport properties. The as-cast samples have low Seebeck coefficients (α300K ≤ 35 μV/K), and are not suitable for thermoelectric applications. The spark plasma sintering procedure did not significantly change the Seebeck coefficient values and can degrade the electrical conductivity, particularly if skinnerite and famatinite are formed. Materials treated by melt spinning/glass-crystallization show higher Seebeck coefficients and often lower electrical resistivity when compared with the as-cast samples, indicating this method as a suitable technique for quick preparation of good thermoelectric tetrahedrites