Realizing synergistic optimization of electrical and thermal transport properties in BiCuSeO ceramics via multi-element doping

In this study, the design of high-entropy alloys (multi-element substitution, Al3+/La3+/Sb3+/Y3+) was used to increase material entropy and improve heat scattering to further reduce thermal conductivity. Concurrently, Ca2+ ion hole doping was used to improve its electrical conductivity. Therefore, a series of Bi 0.92- xAl0.02La0.02Sb0.02Y0.02CaxCuSeO (x = 0, 0.02, 0.06, 0.10, and 0.14) ceramics was prepared using a combination of high-energy ball milling and cold isostatic pressing. The multi-element substitution of Al 0.02 La 0.02 Sb 0.02 Y 0.02 Ca 0.02 in the Bi site resulted in a minimum thermal conductivity of 0.35 Wm- 1K- 1 , which is one-third of that of intrinsic BiCuSeO. Simultaneously, the conductivity increased up to 10-20 times that of intrinsic BiCuSeO, proportional to the amount of Ca2+ doping. Furthermore, the optimum component Bi 0.82 Al 0.02 La 0.02 Sb 0.02 Y 0.02 Ca 0.10 CuSeO exhibited an extremely high power factor of 568.55 mu Wm- 1K- 2 at 773 K, significantly higher than that of pure BiCuSeO (148.7 mu Wm- 1 K- 2 ). Consequently, a peak ZT value of approximately 1.12 was achieved at 773 K, which was 4.48 times higher than that of the pristine BiCuSeO specimen (approximately 0.25). Our findings provide a novel strategy to optimize the thermoelectric properties of BiCuSeO and other materials.