Phase boundary mapping for high thermoelectric performance β-Zn4Sb3 in Zn–In–Sb ternary system

Abstract

Zn4Sb3 with complex structure shows excellent thermoelectric performance in the low temperature region. Herein, three batches of In doped Zn4Sb3 were synthesized and the influence of In dopant and Zn content on the thermoelectric properties of Zn4Sb3 was systematically investigated by using a phase boundary method. The isothermal ternary phase diagram of Zn–In–Sb is explored at 623 K. The solubility limit of In in the single phase region with β-Zn4Sb3 structure is strongly related to the ratio between Zn + In and Sb. In atoms preferentially occupy C interstitial of 48f site in the crystallographic Wyckoff position and Zn deficiency increases the concentration of Zn vacancies on this site, enhancing the solubility limit of In in the system. The modification of structure via doping with In hinders the movement and diffusion of Zn interstitial in Zn4Sb3, accompanying with the disappearance of the low temperature phase transitions from α′ to α phase and from α to β phase. The regulation of Zn and In contents in single phase region with β-Zn4Sb3 structure effectively optimizes the thermoelectric performance. A maximum ZT value of 1.43 is attained at 673 K for (Zn0·96In0.04)4.15Sb3 compound, which demonstrates a 47% improvement in comparison with that of Zn4·15Sb3 compound. This work provides a new avenue to further improve thermoelectric properties of Zn4Sb3 compounds.