Enhanced thermoelectric and mechanical properties of polycrystalline cubic SnSe by AgBiTe2 alloying

Recently, the cubic SnSe with multiple valleys and low thermal conductivity has become the focus of current research and receives extensive attention worldwide. However, the cubic SnSe is difficult to exist stably at normal temperature and pressure. In this work, the cubic rock-salt SnSe samples were successfully stabilized at room temperature by AgBiTe2 alloying. Microstructure and thermoelectric properties of the Sn1–2x(AgBi)xSe1–2xTe2x (x = 0, 0.10, 0.15, 0.20, 0.25, 0.30) were studied systematically. With the increase of AgBiTe2 addition, the crystal structure of SnSe gradually transformed from orthorhombic to cubic phase. Due to the doping of heterogeneous atoms and the phase structural transformation, the carrier concentration and carrier mobility of Sn1–2x(AgBi)xSe1–2xTe2x were optimized, thus the electrical properties were significantly enhanced. An obviously enhanced zTmax of 0.70 at 750 K and a zTave of 0.29 (300–750 K) were achieved in Sn0.50(AgBi)0.25Se0.50Te0.50. In addition, the mechanical properties of Sn1–2x(AgBi)xSe1–2xTe2x were also strengthened. A higher Vickers hardness of ∼1.8 GPa was obtained in Sn0.40(AgBi)0.30Se0.40Te0.60.