High temperature thermoelectric properties of Mo3Sb7?xTex (0.0 ? x ? 1.8)

Polycrystalline Mo3Sb7?xTex samples with nominal Te concentrations of x = 0.0,0.3,1.0,1.6 and 2.2 have been synthesized by a powder metallurgical route. High temperature thermoelectric properties measurements including thermopower (300?900?K), electrical resistivity (300?800?K) and thermal conductivity (300?1000?K) were carried out. The temperature and compositional variations of the thermopower can be satisfactorily explained by assuming a single parabolic band model with dominant acoustic phonon scattering. However, such a simple model fails to describe the electronic thermal conductivity for low Te concentration. The dimensionless figure of merit, ZT, increases on increasing both the temperature and the Te content to reach a maximum value of 0.3 at 800?K that can be extrapolated to ~ 0.6 at 1000?K for Mo3Sb5.4Te1.6.