Spark plasma sintering technique: an alternative method to enhance ZT values of Sb doped Cu₂SnSe₃

Sb doped Cu₂Sn_1−xSb_xSe₃ (0 ≤ x ≤ 0.04) compounds have been fabricated by spark plasma sintering technique for the investigation of their thermoelelctric properties in the temperature range 10–400 K. The conduction mechanism of electrical resistivity reveals that small polaron hopping model is valid in the high-temperature regime and variable range hopping model in low-temperature regime. The positive values of Seebeck coefficient (S) for Cu₂Sn_1−xSb_xSe₃ (0 ≤ x ≤ 0.04) samples in the entire temperature range indicates that the majority charge carriers are holes. The electronic thermal conductivity (κ_e) was estimated by Wiedmann-Franz law and found that the contribution of κ_e to the total κ is < 1%, suggesting that the heat conduction for presently studied Cu₂Sn_1−xSb_xSe₃ (0 ≤ x ≤ 0.04) samples is mainly associated to the lattice phonons. The highest ZT value for the Cu₂Sn_0.96Sb_0.04Se₃ sample was 0.044 at 400 K, which is approximately four times that of the Cu₂SnSe₃ sample and an order of magnitude larger than the samples prepared by the conventional solid-state method. Also, the thermoelectric compatibility factor of Cu₂Sn_0.96Sb_0.04Se₃ was found to be about 1 per V.