Effect of Excess Zn on Thermoelectric Properties of Zn4Sb3

Non-stoichiometric Zn_4+xSb₃ specimens with x = 0.1-0.4 were prepared by vacuum melting at 1173 K and subsequent annealing the solidified ingots at 623 K. The effects of excess Zn on the microstructure and the thermoelectric properties of Zn_4+xSb₃ were investigated. Zn phase was found to be precipitated in Zn_4+xSb₃ with x = 0.1-0.4 due to excess Zn in Zn₄Sb₃ structure. As x increased from x = 0.1 to x = 0.4, both Seebeck coefficient and electrical resistivity decreased, while thermal conductivity increased due to the formation of metallic Zn phase as well as the increase of the carrier concentration. Carrier concentration of Zn_4+xSb₃ increased from 1.37 times 10²⁰cm^-3 to 4.95 times 10²⁰cm^-3 with increasing x from 0.1 to 0.4. Maximum ZT of 1.2 was obtained in Zn_4.1Sb₃ at 600 K with Seebeck coefficient of 174 muV K^-1, electrical resistivity of 2.18 mOmega cm, and thermal conductivity of 7.07 mWcm ^-1K^-1