Improving thermoelectric performance of NbCo1.1SnSb0.1 with grain size refinement via ball milling induced crystallization

Abstract

NbCoSn-based half-heusler thermoelectric materials are promising materials for next-generation eco-friendly energy that not only have excellent mechanical properties and thermal stability but also consist of low-cost elements compared to other thermoelectric materials, showing advantages. However, the high thermal conductivity of the material contributes to the low value of the Figure of merit, ZT, which represents the thermoelectric performance, and is limited in its practical use. We performed a study to reduce thermal conductivity by forming ultra-fine grain size of NbCo$_{1.1}$SnSb$_{0.1}$ Heusler thermoelectric materials. Ball milling of the amorphous NbCo$_{1.1}$Sn ribbon formed NbCo$_2$Sn full Heusler nanocrystals for the formation of heterogeneous nucleation sites, which were confirmed by the Atom probe tomography, STEM, and correlative research. In addition, Sb doping increased the electrical conductivity to obtain a ZT value of 0.57. We expect this study of grain size refinement via ball milling of amorphous alloys can be applied to other thermoelectric materials for improving ZT.