Enhancement in the thermoelectric properties of Cu₃SbSe₄ by Sn doping

The solid-state reaction technique was employed to fabricate Sn doped Cu₃SbSe₄ samples. The effect of doping on structural and thermoelectric properties of Cu₃SbSe₄ samples is represented in the present communication. The powder X-ray diffraction pattern of all the samples show that they have tetragonal structure (space group I4 ¯ 2 m). It is observed that doping Sn at Sb site acts as acceptor dopant which enhances hole concentration. The temperature dependent electrical resistivity (ρ(T)) is observed to decrease with increase in Sn concentration up to x = 0.03, thereafter ρ(T) increases with the increase in x concentration. To explore the conduction mechanism, we have employed small poloron hopping (SPH) model to the ρ(T) data and the results indicate that SPH is operative in the high temperature regime for all samples. The data of Seebeck coefficient (S(T)) confirms that holes are the majority charge carriers for pristine as well as doped samples. The analysis of S(T) data reveals that all the samples have a narrow band gap. The contribution from electron thermal conductivity is found to be less than 1%, thus the total conductivity is mainly because of phonon thermal conductivity. The highest value of dimensionless figure of merit (ZT = 0.127) was achieved at 374 K for the sample Cu₃Sb_0.99Sn_0.01Se₃ which is slightly higher than that of the pristine sample (ZT = 0.115). The highest value of compatibility factor (0.98 V⁻¹) was observed for the sample Cu₃Sb_0.98Sn_0.02Se₃ at 374 K.