Abstract
Lead-free SnTe with naturally non-stoichiometric vacancies has a limited thermoelectric performance due to a deviated carrier concentration from the optimum. In this paper, we experimentally demonstrated that Gd with + 3 valence state as a novel n-type dopant is an effective solution for reducing carrier concentration in SnTe. A lowest value of 7.6 x 1018 cm-3 has been achieved. Yet with the involvement of Gd doping, the slightly modified band structure requires a further Sn-deficiency compensation to enhance the overall figure of merit zT. As a consequence, in the specific sample Sn0.91Gd0.07Te, we successfully achieved a low lattice thermal conductivity of 0.8 W/(m K) due to the high doping level and an improved zT approaching 0.8 at 850 K.