Effects of a Cu-contained compound on the microstructures and thermoelectric properties of Zn–Sb based alloys

Zn–Sb based alloys with Cu2Sb addition were prepared using spark plasma sintering technique and the effects of a Cu-contained intermetallic phase on the microstructures and thermoelectric properties were examined. Rietveld refinement reveals that there are many phases in the alloys, which involve β-Zn4Sb3, a major phase ZnSb, a small amount of an intermetallic compound Cu5Zn8 and unidentified impurity phases, the quantities of ZnSb and Cu5Zn8 increase from 67.3 wt.% to 91.8 wt.% and 0–4.3 wt.% with Cu2Sb additive increasing, respectively. The ZnSb plays a fundamental role in controlling the thermoelectric properties, and Cu5Zn8 is of great significance to optimize the transport properties. The maximum thermoelectric figure of merit ZT of 0.72 is obtained for the alloy (Cu2Sb)0.05–(Zn4Sb3)0.95 at 654 K, which is 0.25 higher than that of undoped β-Zn4Sb3 at the same conditions. Therefore, we conclude that a proper addition of Cu2Sb can contribute to the improvement of thermoelectric properties of Zn–Sb based alloys.