Enhanced thermoelectric performance through carrier scattering at spherical nanoparticles in Bi0.5Sb1.5Te3/Ta2O5 composites

The greatest challenge is to elevate the thermoelectric figure of merit of existing materials via enhancing their power factor and reducing the thermal conductivity using nanocomposite approach. In this work, Bi0.5Sb1.5Te3 (BST) based composites dispersed with new type of insulating Ta2O5 nanoparticles (NPs) were fabricated using high energy ball milling and spark plasma sintering, and their thermoelectric properties were investigated. The existences of NPs in the matrix were systematically investigated using SEM, EPMA and TEM analysis. The results indicate that the Seebeck coefficient significantly increased (50%) and less reduction in electrical conductivity with the addition of Ta2O5 content due to the decreased carrier concentration and the enhanced carrier scattering by the newly created interfaces between spherical NPs and matrix. Simultaneously, the thermal conductivity (κ) decreased substantially with the addition of NPs, which is 25% lower than BiSbTe matrix owing to enhanced carrier scattering at NPs. As a result, the highest ZT value obtained was 1.38 at 300 K for the incorporation of 4 wt% Ta2O5 NPs in Bi0.5Sb1.5Te3 matrix. These results enable that the thermoelectric performance of BST composites can be effectively improved with the addition of Ta2O5 NPs.