The effects of iodine doping on the thermoelectric properties of at low temperatures

The thermoelectric properties of iodine-doped compounds Zn4(Sb1−xIx)3 ( x = 0 , 0.005, 0.01, 0.015) have been studied at temperatures from 5 to 310 K. The results indicate that the low-temperature ( T < 300 K ) thermal conductivity λ of moderately doped Zn4(Sb0.995I0.005)3 reduced remarkably as compared with that of Zn4Sb3 due to the enhanced impurity (dopant) scattering of phonons. The electrical resistivity and Seebeck coefficient were found to increase monotonically with the increase in the iodine content, which would reflect the decrease in carrier concentration due to the substitution of I for Sb. Moreover, the lightly doped compound Zn4(Sb0.995I0.005)3 exhibited the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient. Its figure of merit, ZT, was about 1.2 times larger than that of β - Zn4Sb3 obtained in the present study at 300 K.