Thermoelectric properties of non-stoichiometric β-Zn _3:83+δSb₃ polycrystals sintered by a hot-press method

In a moderate temperature range (450-650 K), β-Zn _3:83+δSb₃ has numerous advantages because the figure-of-merit (ZT) of β-Zn_3:83+δSb₃ is the highest in this temperature range. However there are difficulties when attempting to control the stoichiometry so as to manufacture Zn _3:83+δSb₃ specimens. In this study, three different compositions, Zn_3:83Sb₃ [δ (excess Zn) = 0], Zn _3:9Sb₃ (δ = 0:07), and Zn₄Sb₃ (δ = 0:17), were designed to obtain a β-Zn _3:83+δSb₃ single phase through a hot-press sintering process. An investigation for the temperature dependence of thermoelectric properties confirmed that the Zn₄Sb₃ (δ = 0:17) composition hot-pressed at 723 K was the optimized condition for obtaining the Zn_3:83+δSb₃ single phase representing best thermoelectric properties. As a result, a maximum ZT value of 1.33 was obtained at a measuring temperature of 664 K for the Zn₄Sb₃ (δ = 0:17) composition hot-pressed at 723 K.