Ge-doped Sb100GeTe150 alloy were prepared using spark plasma sintering technique, and its thermoelectric properties were evaluated over the temperature range 318-492 K. Through XRD analysis, we observed the same single phase as Sb2Te3 and weakened diffraction peaks. Rietveld refinement reveals that there is 0.96 at.% Ge that occupies in the Sb sites, leading to the lattice distortion in the Sb-Te crystal. High-resolution TEM images show that there are many nanodomains randomly distributed in the matrix with a large amount of amorphous phase adjoined. Measurements indicated that the Seebeck coefficients (alpha) increase and the electrical and thermal conductivities decrease with temperature in the entire temperature range. The maximum alpha value reaches 135 mu V/K at 492 K, and the thermal conductivities are about 0.3 W/mK lower than those of present Sb2Te3 for the corresponding temperatures. The highest thermoelectric figure of merit ZT for the nanostructured alloy Sb100GeTe150 is 0.84 at 492 K, whereas that of the currently prepared Sb2Te3 is 0.74 at the corresponding temperature. (C) 2009 Elsevier B.V. All rights reserved.