Effect of heavy doping of nickel in compound Mo3Sb7: Structure and thermoelectric properties

Thermoelectric properties of nickel-heavily-doped Mo3Sb7 compounds (NixMo3−yNiySb7, x + y = 0.00, 0.15, 0.20, 0.25 and 0.30), obtained via a metallurgical route, are reported. Structural analysis by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) suggest that most Ni atoms are inserted into the cubic voids while the remaining a few substitute Mo atoms. Ni in the cubic voids increases the densities and the slope of electronic states near Fermi level, resulting in the increase of electrical conductivity (σ) and thermopower (α). Meanwhile, Ni at the substituted sites induces phonon-scattering disorder in the crystal, leading to the decrease of the thermal conductivity (κ). These results indicate that the simple heavy-Ni-doping could provide a unique way to optimize all the thermoelectric parameters in this Mo3Sb7 compound.