Résumé
Lead chalcogenides PbX (X = Te, Se, S) have been the materials of choice for thermoelectric power generation at mid-range temperatures (500–700 K). Here, we report on a new family of chalcogenides α-As2Te3 that exhibit similar thermoelectric performances near 500 K. Sn doping in p-type polycrystalline α-As2−xSnxTe3 (x ≤ 0.075) provides an efficient control parameter to tune the carrier concentration leading to thermopower values that exceed 300 μV K−1 at 500 K. Combined with the structural complexity of the monoclinic lattice that results in extremely low thermal conductivity (0.55 W m−1 K−1 at 523 K), a peak ZT value of 0.8 is achieved at 523 K for x = 0.05. A single-parabolic band model is found to capture well the variations in the transport properties with the Sn concentration and suggests that higher ZT values could be achieved through band structure engineering. These results surpass those obtained in the sister compounds β-As2−xSnxTe3 and further show that α-As2Te3 based materials are competitive with other chalcogenides for thermoelectric applications at intermediate temperatures.