Synergistic modulation of phonon and charge transport in rare-earth Sm-doped Cu₂SnSe₃ thermoelectric system

Cu₂SnSe₃ has attracted a lot of attention as a potential thermoelectric material due to the distinct electrical and thermal characteristics. We report the effect of samarium doping on the Sn site Cu₂SnSe₃ system. Polycrystalline Cu₂Sn_1-xSm_xSe₃ (0 ≤ x ≤ 0.08) samples were synthesized by the solid-state method followed by traditional sintering. The low-temperature range of 10–350 K was used to study the electrical transport properties. The lowest resistivity of 0.0024 Ω-cm at 350 K was exhibited by x = 0.08 sample. All the samples’ Seebeck coefficients were found to be positive within the temperature range under investigation, suggesting that most of the charge carriers are holes. With increasing Sm concentration, the resistivity and Seebeck coefficient gradually decreased showing degenerate semi-conducting behaviour. The thermal conductivity also decreased with increasing doping concentration due to the induced defects which enhances the phonon scattering in the Cu₂SnSe₃ system. Overall, a maximum ZT of 0.017 was achieved for x = 0.08 at 350 K.