Structural and physical properties of Mg 3−xZn xSb 2 ( x=0–1.34)

Abstract

The Mg 3− x Zn x Sb 2 phases with x=0–1.34 were prepared by direct reactions of the elements in tantalum tubes. According to the X-ray single crystal and powder diffraction, the Mg 3− x Zn x Sb 2 phases crystallize in the same P3¯ m1 space group as the parent Mg 3Sb 2 phase. The Mg 3− x Zn x Sb 2 structure is different from the other substituted structures of Mg 3Sb 2, such as (Ca, Sr, Ba) Mg 2Sb 2 or Mg 5.23Sm 0.77Sb 4, in a way that in Mg 3− x Zn x Sb 2 the Mg atoms on the tetrahedral sites are replaced, while in the other structures Mg on the octahedral sites is replaced. Thermoelectric performance for the two members of the series, Mg 3Sb 2 and Mg 2.36Zn 0.64Sb 2, was evaluated from low to room temperatures through resistivity, Seebeck coefficient and thermal conductivity measurements. In contrast to Mg 3Sb 2 which is a semiconductor, Mg 2.36Zn 0.64Sb 2 is metallic and exhibits an 18-times larger dimensionless figure-of-merit, ZT, at room temperature. However, thermoelectric performance of Mg 2.36Zn 0.64Sb 2 is still poor and it is mostly due to its large electrical resistivity.