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

Abstract

The prototype phonon-liquid electron-crystal β-Cu₂Se 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_0.001Cu₂Se 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 Bi_0.001Cu₂Se_0.90Te_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_0.001Cu₂Se alloy. Both Bi_0.001Cu₂Se and Bi_0.001Cu₂Se_0.90Te_0.10 demonstrated comparable high power factors of 1221.9 μWm^− 1K^− 2 and 1223.6 μWm^− 1K^− 2, attributed to their moderate electronic conductivity and Seebeck coefficient. The porous Bi_0.001Cu₂Se_0.80Te_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_0.001Cu₂Se 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 Bi_0.001Cu₂Se_0.80Te_0.20 was found to have a maximum value of approximately 1.49 at 873 K, primarily due to its significantly lower thermal conductivity.