Effects of Cu5Zn3 addition on the thermoelectric properties of Zn4Sb3

Abstract

The structures and thermoelectric properties of mCu5Zn3⋅nZn4Sb3 with multiphase coexistence are reported. Rietveld analysis reveals that at least 92.3% wt % β-Zn4Sb3 phase can be obtained with only small quantities of ZnSb and Cu5Zn8 phases precipitated after proper Cu5Zn3 addition. Measurements indicate that although the β-Zn4Sb3 phase plays a determining role in controlling the transport properties involving the Seebeck coefficient, electrical conductivity, and thermal conductivity, the impurity phases Cu5Zn8 and ZnSb with a crooked riverlike and intertwined tree stump morphologies, respectively, are still of great significance to tune the thermoelectric performance. The highest ZT value of 0.84 can be obtained for the alloy mCu5Zn3⋅nZn4Sb3 (m/n=1/200) at 631 K, approximately 1.8 times that of undoped β-Zn4Sb3, proving that a good combination between the transports of carriers and phonons can be achieved if a proper dopant is introduced in the Zn4Sb3 matrix.