Enhancing the thermoelectric performance of CoSb3-based skutterudite by decoupling the electrical and thermal properties by embedding Cu nanoparticles

Co_0.91Ni_0.09Sb₃ embedded with Cu nanoparticles (NPs) was synthesized by applying a hydrothermal process followed by spark plasma sintering. The effects of Cu NPs on the electrical and thermal transport properties of the Co_0.91Ni_0.09Sb₃ matrix were investigated in the temperature range of 303–773 K. Cu NPs introduced into the Co_0.91Ni_0.09Sb₃ matrix slightly decreased the electrical conductivity and significantly enhanced the Seebeck coefficient by the energy filtering effect, leading to an improved power factor at 773 K. Furthermore, a significant decrease in the thermal conductivity was realized by increasing the number of grain boundaries. These favorable effects contributed to the improvement in ZT to a value ~57% higher than that of pristine Co_0.91Ni_0.09Sb₃. The highest ZT value of 1.02 was achieved by incorporating 4.5 wt% of Cu NPs in Co_0.91Ni_0.09Sb₃ at 773 K. Thus, decoupling the electrical and thermal transport properties of thermoelectric materials is a viable strategy for optimizing the ZT value.