The Effect of Secondary Phase on Thermoelectric Properties of Zn$_{4}$Sb$_{3}$ Compound

Zn$_{4}$Sb$_{3}$ is a promising thermoelectric material because of its high thermoelectric performance and the abundance of Zn and Sb in nature. Samples of Zn$_{4}$Sb$_{3}$ with ZnSb or Zn as the minor phase were prepared to optimize the figure-of-merit (\textit{ZT}). The effects of ZnSb or Zn secondary phase on the thermoelectric properties of Zn$_{4}$Sb$_{3}$ were investigated. The highest peak \textit{ZT} of about 1.3 was achieved at 400 $^{o}$C in the sample with single Zn$_{4}$Sb$_{3}$ phase, which has the lowest thermal conductivity. Transmission electron microscopy observations of the nanostructures suggest that the precipitated ZnSb, Zn-rich nanoparticles, and nano voids, caused by volatile Zn diffusion, all contribute to the extraordinarily low thermal conductivity.