Effects of Bi doping on the thermoelectric properties of β-Zn4Sb3

The thermoelectric properties of Bi-doped compounds (Zn1-xBix)(4)Sb-3 (x=0,0.0025,0.005,0.01) were studied experimentally as well as theoretically. The results indicate that low-temperature (T < 300 K) thermal conductivity of moderately doped (Zn0.9975Bi0.0025)(4)Sb-3 reduces remarkably as compared with that of Zn4Sb3 due to enhanced phonon scattering of impurity (dopant). Electrical resistivity and Seebeck coefficient increase monotonically with increase in the Bi content resulting mainly from decrease in carrier concentration. Moreover, first-principle calculations were performed on the occupation options of Bi atoms in beta-Zn4Sb3, which show that Bi will preferentially occupy the Zn sites and not Sb sites and act as donors, being consistent with the experimental observations. In addition, the lightly doped compound (Zn0.9975Bi0.0025)(4)Sb-3 exhibits the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient, whose figure of merit, ZT, is about 1.5 times larger than that of beta-Zn4Sb3 at 300 K. (C) 2011 American Institute of Physics. [doi:10.1063/1.3544479]