Thermoelectric properties and electronic structure of Te-doped CoSb3 compounds

Co4Sb12−xTex compounds were prepared by mechanical alloying combined with cold isostatic pressing, and the effects of Te doping on the thermoelectric properties were studied. The electronic structure of Te-doped and undoped CoSb3 compounds has been calculated using the first-principles plane-wave pseudo-potential based on density functional theory. The experimental and calculated results show that the value of the solution limit x of Te in Co4Sb12−xTex compounds is between 0.5 and 0.7. The Fermi surface of CoSb3 is located between the conduction band and the valence band, and its electrical resistivity decreases with increasing temperature. The density of states is mainly composed of Co 3d and Sb 5p electrons for intrinsic CoSb3.The Fermi surface of Te-doped compounds moves to the conduction band and its electrical resistivity increases with increasing temperature, exhibiting n-type degenerated semiconductor character. Under the conditions of the experiment, the maximum value 2.67 mW/m K2 of the power factor for Co4Sb11.7Te0.3 is obtained at 600 K; this is about 14 times higher than that of CoSb3.