High thermoelectric performance of BiCuSeO by optimized carrier concentration and point defect scattering through a Cr-induced compositing effect

Abstract

BiCuSeO has intrinsically low electrical conductivity, a high Seebeck coefficient, and low thermal conductivity. Therefore, the improvement of the thermoelectric performance of BiCuSeO mainly focuses on enhancing its electrical conductivity. In this study, we report the high thermoelectric performance of BiCuSeO achieved by optimizing the carrier concentration and phonon scattering through the composite effect induced by Cr addition. The enhanced electrical conductivity coupled with a moderate Seebeck coefficient leads to an almost one order of magnitude improvement of the power factor from ∼0.07 mW m⁻¹ K⁻² for the pristine BiCuSeO to ∼0.57 mW m⁻¹ K⁻² for the BiCu_0.96Cr_0.04SeO sample at 473 K. The Cr addition reduces the lattice thermal conductivity by ∼23%, as confirmed by both experimental results and Debye–Callaway model calculations. The analysis indicates that the lattice thermal conductivity can be reduced to 0.5 W m⁻¹ K⁻¹ at 773 K due to enhanced point defect scattering. The combination of optimized power factor and intrinsically low thermal conductivity yield a relatively high zT. The maximum zT value of ∼0.7 is obtained at 773 K for the BiCu_0.96Cr_0.04SeO sample. This study demonstrates the potential of utilizing the compositing approach for the development of efficient thermoelectric materials based on BiCuSeO oxyselenides.