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 W 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 approximate to 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.