Effects of Ag doping on thermoelectric properties of Zn4Sb3 at low temperatures

The thermoelectric properties of Ag-doped compounds (Zn1−xAgx)4Sb3 (x = 0, 0.0025, 0.005, 0.01) have been studied at the temperatures from 15 to 300 K. The results indicate that low-temperature (T < 300 K) thermal conductivity of the moderately doped (Zn1−xAgx)4Sb3 (x = 0.0025 and 0.005) reduced remarkably as compared with that of Zn4Sb3 due to enhanced impurity (dopant) scattering of phonons. Electrical resistivity and Seebeck coefficient were found to increase first and then decrease obviously with the increase in the Ag content, which could be ascribed to the change of carrier concentration presumably due to different Zn positions occupied by Ag upon increasing doping content. Moreover, the lightly doped compound (Zn0.995Ag0.005)4Sb3 exhibited the best thermoelectric performance due to the improvement in both its electrical resistivity and thermal conductivity, whose figure of merit (at 300 K), ZT, is about 1.3 times larger than that of β-Zn4Sb3 obtained in the present study. Present results suggest that proper Ag doping in Zn4Sb3 is a promising way of improving its thermoelectric properties.