Thermoelectric properties of textured polycrystalline Na0.03Sn0.97Se enhanced by hot deformation

Tin selenide (SnSe) has attracted widespread attention due to the high thermoelectric figure of merit (ZT ≥ 2) in its single crystals, while polycrystalline SnSe shows moderate thermoelectric performance due to its electrical properties. In this study, a hot deformation process was applied to prepare a dense and textured Na-doped SnSe polycrystalline sample in a hot-press. The hot deformed samples exhibit excellent grain alignment, which increases their electrical conductivity to 148 S cm−1 at 823 K, leading to a maximum power factor of up to 10.2 μW cm−1 K−2 at 823 K. Moreover, the hot deformation procedure tends to increase the grain size, which could induce a high thermal conductivity. A peak ZT of ∼1.3 was obtained at 793 K for hot deformed Na0.03Sn0.97Se compared with that of 0.7 for the sample processed by the conventional hot pressing method at a similar temperature. The present study indicates that the texture modulation by hot deformation can lead to a great enhancement in the electrical performance in polycrystalline SnSe compounds.