High-Performance and Stable (Ag, Cd)-Containing ZnSb Thermoelectric Compounds

Binary Zn-Sb-based compounds, ZnSb and Zn4Sb3, are promising thermoelectric (TE) materials because they are low-cost and earth-abundant. However, for a long time, their real applications have been limited by the low TE figure-of-merit (zT) of ZnSb and poor thermodynamic stability of Zn4Sb3. In this study, we successfully integrate both high zT and good stability in (Ag, Cd)-containing ZnSb compounds. Alloying Cd in ZnSb greatly suppresses the lattice thermal conductivity to a minimum value of 0.97 W K-1 m(-1) at 300 K, while doping Ag significantly enhances the power factor to a peak value of 17.7 mu W cm(-1) K-2 at 500 K and reduces the bipolar thermal conductivity. As a result of the simultaneously optimized electrical and thermal transport, a peak zT of 1.2 is achieved for Zn0.698Ag0.002Cd0.3Sb at 600 K, which is comparable with the best values reported for Zn4Sb3-based compounds. Moreover, a current stress test confirms that introducing Ag and Cd does not degrade the good stability of ZnSb under an electric field. The phase composition and thermoelectric performance of Zn0.698Ag0.002Cd0.3Sb are not changed even under a high current density of 50 A cm(-2), showing much better stability than Zn4Sb3. This study would accelerate the real application of ZnSb-based compounds in the field of waste heat harvesting.