Effects of Sb on the Charge Transport and Power Factor of Bi2-xSbxTe3 Thermoelectric Compounds Prepared by Hot Pressing

We report the effects of Sb content on the charge transport and power factor of Bi2-xSbxTe3(1.56 <= x <= 1.74) compounds prepared by hot pressing. From the temperature-dependence of the electrical conductivity, it was found that the charge transport in the compounds was predominantly governed by acoustic phonon scattering, and additionally affected by ionized impurity scattering. Hole concentration increased with increasing Sb content due to the generation of antisite defects, and its process-dependence is discussed in comparison with our previous work. The room-temperature mobility of the compound gradually decreased with increasing Sb content due to the intensification of ionized impurity scattering by the antisite defects, however, the effect of grain boundary scattering on the mobility could not be observed. The Seebeck coefficient decreased with the increase in Sb content, and this effect was interpreted in terms of the carrier concentration and the density-of-state (DOS) effective mass. The DOS effective mass was estimated by Pisaernko relation, and it increased from 0.75 (x = 1.56) to 0.97 (x = 1.74) with increasing Sb content due to the non-parabolicity in the valence band of Bi2-xSbxTe3. Based on these results, the effects of Sb content on the power factor were discussed, and the highest power factor of 37.2 x 10(4) Wm(-1)K(-2) was obtained in the Bi0.3Sb1.7Te8 compound at room temperature.