Studies on thermoelectric figure of merit of Na-doped p-type polycrystalline SnSe

Abstract

SnSe has attracted some attention due to the recent report of record high thermoelectric figure-of-merit (ZT) of ∼2.6 at about 923 K in single crystals. Even though the ZT is high in single crystal SnSe, it was very low in its polycrystalline form due to the very low electrical conductivity (<10³ S m⁻¹) from 300 K to 700 K. In this work, we report studies on enhancement of electrical conductivity by Na doping to optimize the carrier concentration in polycrystalline SnSe prepared by melting and hot pressing. A room temperature carrier concentration of ∼2.7 × 10¹⁹ cm⁻³ was obtained in 2 atm% Na-doped SnSe samples with the highest power factor obtained in 1.5 atm% Na-doping. A peak ZT of ∼0.8 was achieved at 773 K along the hot pressing direction and the average ZT was improved.