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Description
Currently available commercial thermoelectric generators contain expensive and potentially hazardous elements, such as Bi, Pb or Te. To overcome this hindrance, the application of alternative materials, like the p-type semiconductor mineral tetrahedrite (Cu12Sb4S13), is being studied. Tetrahedrite is a naturally occurring and abundant mineral with low toxicity that displays good electrical and thermal properties, with a figure of merit, zT, of 0,6 at 700K. Comparatively to commercially available thermoelectric materials (zT>1,0), tetrahedrite still has a small zT, but various studies suggest that it can be increased via isovalent doping. [1]
The objective of this project is to study the effect of selenium (Se) and nickel (Ni) or chromium (Cr) simultaneous isovalent doping in the thermoelectric properties of tetrahedrite. Powder X-Ray Diffraction, Raman Spectroscopy and Scanning Electron Microscopy, with Energy Dispersive Spectrometry, were used in the characterization of Cu12-xMxSb4S13-ySey, (M= Ni or Cr). After annealing at 723K for 7 days (the current stage of the production process), the samples show a main tetrahedrite phase (with the lowest ≈84% molar content), and a minor presence of secondary phases. Measurements of the Seebeck coefficient and electrical resistivity, suggest that doping improves the power factor, with the Cu11,5Ni0,5Sb4S12,5Se0,5 sample achieving the highest value of 1277,73 µW/m.K2 at 300K. After estimation of thermal conductivity with the Friedman-Franz law, a figure of merit zT=0.32 at 300K (Fig. 1 and 2) was obtained.
