Doping telluride for tuning the crystal structure and thermoelectric performance of copper selenide-based materials

The prototype phonon-liquid electron-crystal β-Cu 2 Se has been recognized as one of the top-performing thermoelectric materials due to its ultralow lattice thermal conductivity (κ ). This paper reports the synthesis of Telluride-doped Bi 0.001 Cu 2 Se through the combination of ball milling and spark plasma sintering. The thermoelectric properties of the materials, encompassing electrical resistivity, Seebeck coefficient, and thermal conductivity within the temperature range of 300 K to 873 K, have been evaluated. The Bi 0.001 Cu 2 Se 0.90 Te 0.10 sample exhibited a peak Seebeck coefficient of 192.6 μV/K, which is approximately 23.5% higher than that of the bulk Bi 0.001 Cu 2 Se alloy. Both Bi 0.001 Cu 2 Se and Bi 0.001 Cu 2 Se 0.90 Te 0.10 demonstrated comparable high power factors of 1221.9 μWm − 1 K − 2 and 1223.6 μWm − 1 K − 2 , attributed to their moderate electronic conductivity and Seebeck coefficient. The porous Bi 0.001 Cu 2 Se 0.80 Te 0.20 samples exhibited a minimum thermal conductivity of 0.61 − 1  K − 1 at 873 K, representing a reduction of up to 21.8% compared to the bulk Bi 0.001 Cu 2 Se alloy. This decrease in thermal conductivity can be attributed to the boundaries and defects formed during the spark plasma sintering process, as well as the porous nature of the samples. The figure of merit for the Bi 0.001 Cu 2 Se 0.80 Te 0.20 was found to have a maximum value of approximately 1.49 at 873 K, primarily due to its significantly lower thermal conductivity.