The influence of bismuth (Bi) substitution on the thermoelectric properties of AgSbTe 2 compounds was investigated and compared with the undoped AgSbTe 2 . The addition of Bi dopants not only resulted in a reduction in thermal conductivity but also markedly increased the thermopower in the Ag(Sb 1Àx Bi x)Te 2 series. Additional phonon scatterings were created by Bi doping and led to a reduction of thermal conductivity. The lattice thermal conductivity is significantly reduced which could be ascribed to enhancement of phonon scattering by dopants with greater atomic weight. In addition, the thermopower was enhanced, which was attributed to the electron-filtering effects caused by the nanoscaled microstructures. Because of the extremely low thermal conductivity (0.48 Wm À1 K À1) and moderate power factor of AgBi 0.05 Sb 0.95 Te 2 , a maximum ZT value of (1.04 6 0.08) was reached at 570 K; yielding an enhancement of greater than 10% compared with an undoped AgSbTe 2 . this result shows promising thermoelectric properties in the medium temperature range. V C 2013 AIP Publishing LLC.