Synthesis and high temperature transport properties of Te-doped skutterudite compounds

Te-doped skutterudite compounds Co₄Sb_12?x Te _x (x?=?0.4–0.7) have been fabricated by solid state reaction method and spark plasma sintering. The scanning electron microscope images indicate all samples are compact and the average particle size increases with the Te doping fraction. The carrier concentration and electrical conductivity exhibit positive doping fraction dependence, and a maximum electrical conductivity of 16.29?×?10⁴?Sm^?1 is obtained at 300?K for Co₄Sb_11.3Te_0.7. The values of the power factor (x?=?0.4–0.6) are greater than 4.0?×?10^?3?Wm^?1?K^?2 at the temperature range of 650–800?K, larger than previous literature reports. The lattice thermal conductivity decreases monotonously over the whole investigated temperature range and exhibits a negative doping fraction dependence except for Co₄Sb_11.3Te_0.7. The resultant dimensionless figure of merit of all the samples increases monotonously over the whole investigated temperature range, and a maximum value of 0.95 is achieved at 800?K for Co₄Sb_11.4Te_0.6.