Enhanced power factor and thermoelectric efficiency in Cu₂Sn_{1- x}Y_xSe₃ system: A low-temperature study

In the present study, we report the effect of Y doping at the Sn-site on structural, electrical, and low-temperature (10–350 K) thermoelectric properties of the Cu₂SnSe₃ system. The bulk polycrystalline samples of Cu₂Sn_1-xY_xSe₃ (0 ≤ x ≤ 0.12) are synthesized by the conventional solid-state reaction route method. Rietveld analysis of room temperature XRD data confirmed that the studied samples possess cubic crystal structure with F4‾3m space group. Temperature-dependent electrical resistivity of the samples with x ≤ 0.04 shows that they exhibit semiconducting behavior; while samples with x > 0.04 exhibit metallic behavior. In the studied temperature range, the Seebeck coefficient for all the samples is found to be positive, indicating that the majority of charge carriers are holes. A significant reduction in the electrical resistivity leads to an enhancement in the power factor, attaining a value of ∼253 μW/mK² for the sample with x = 0.12 at 350 K. At high temperatures, the thermal conductivity of the samples decreases with temperature which is attributed to the phonon-phonon scattering. The systematic evolution of thermoelectric properties with Y incorporation over the range (0 ≤ x ≤ 0.12) shows the highest ZT of 0.024 at 350 K for the sample with x = 0.10, which is about six times higher than that of the pristine Cu₂SnSe₃. The results demonstrate that Y-doped compounds Cu₂Sn_1−xY_xSe₃ are potential candidates for thermoelectric applications.