Enhancement of thermoelectric figure of merit in β-Zn_4Sb_3 by indium doping control

摘要

We demonstrate the control of phase composition in Bridgman-grown β-Zn_4Sb_3 crystals by indium doping, an effective way to overcome the difficulty of growing very pure β-Zn_4Sb_3 thermoelectric material. The crystal structures are characterized by Rietveld refinement with synchrotron X-ray diffraction data. The results show an anisotropic lattice expansion in In-doped β-Zn_4Sb_3 wherein the zinc atoms are partially substituted by indium ones at 36f site of R-3c symmetry. Through the elimination of ZnSb phase, all the three individual thermoelectric properties are simultaneously improved, i.e., increasing electrical conductivity and Seebeck coefficient while reducing thermal conductivity. Under an optimal In concentration (x = 0.05), pure phase β-Zn_4Sb_3 crystal can be obtained, which possesses a high figure of merit (ZT) of 1.4 at 700 K.