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

The prototype phonon-liquid electron-crystal beta-Cu2Se has been recognized as one of the top-performing thermoelectric materials due to its ultralow lattice thermal conductivity (kappa ). This paper reports the synthesis of Telluride-doped Bi0.001Cu2Se 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 Bi0.001Cu2Se0.90Te0.10 sample exhibited a peak Seebeck coefficient of 192.6 mu V/K, which is approximately 23.5% higher than that of the bulk Bi0.001Cu2Se alloy. Both Bi0.001Cu2Se and Bi0.001Cu2Se0.90Te0.10 demonstrated comparable high power factors of 1221.9 mu Wm- 1K- 2 and 1223.6 mu Wm- 1K- 2, attributed to their moderate electronic conductivity and Seebeck coefficient. The porous Bi0.001Cu2Se0.80Te0.20 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 Bi0.001Cu2Se 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 Bi0.001Cu2Se0.80Te0.20 was found to have a maximum value of approximately 1.49 at 873 K, primarily due to its significantly lower thermal conductivity.