Effect of Excess Zn on Thermoelectric Properties of Zn4Sb3

Non-stoichiometric Zn
_4+x
Sb
₃
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+x
Sb
₃
were investigated. Zn phase was found to be precipitated in Zn
_4+x
Sb
₃
with x = 0.1-0.4 due to excess Zn in Zn
₄
Sb
₃
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+x
Sb
₃
increased from 1.37 times 10
²⁰
cm
^-3
to 4.95 times 10
²⁰
cm
^-3
with increasing x from 0.1 to 0.4. Maximum ZT of 1.2 was obtained in Zn
_4.1
Sb
₃
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
^-1
K
^-1