Influence of vanadium oxides nanoparticles on thermoelectric properties of an N-type Mg2Si0.888Sn0.1Sb0.012 alloy

Vanadium oxide nanoparticles were synthetized through a wet chemistry route. Monoclinic VO2 and V2O5 nanoparticles were obtained from synthetized VO2 nanoparticles through different thermal treatments. Monoclinic VO2 phase has attracted a great interest due to it shows a fully reversible first-order metal-to-insulator transition. It is accompanied by very little change in thermal conductivity and an abrupt jump by nearly two orders of magnitude in electrical conductivity. Taking it into account, the influence of vanadium oxide nanoparticles in the thermoelectrical properties of n-type Mg2Si0.888Sn0.1Sb0.012 materials was studied. Composites with different types and several concentration of vanadium oxide were prepared by ball milling and spark plasma sintering. Field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy and x-ray diffraction showed the good dispersion of vanadium oxides nanoparticles into Mg2Si0.888Sn0.1Sb0.012 matrix. An important enhancement in composite contain monoclinic VO2 nanoparticles, by around 38% of figure of merit, was observed compared to the Mg2Si0.888Sn0.1Sb0.012. This improvement of ZT could be attributed to metal-to-insulator transition of monoclinic VO2 phase but further studies should be carried out in order to understand deeply its influence in the thermoelectrical properties of composites. On the other hand, these results show the strong potential of vanadium dioxide nanoparticles as additives to produce a new family of thermoelectric materials.