Transport properties of the layered Zintl compound SrZnSb2

Abstract

Transport properties of the layered Zintl compound SrZn Sb2 have been characterized from room temperature to 725 K on polycrystalline samples. SrZn Sb2 samples were found to be p -type with a Hall carrier concentration of 5× 1020 cm-3 at room temperature, and a small Seebeck coefficient and electrical resistivity are observed. A single band model predicts that, even with optimal doping, significant thermoelectric performance will not be achieved in SrZn Sb2. A relatively low lattice thermal conductivity is observed, κL ∼1.2 W m-1 K-1, at room temperature. The thermal transport of SrZn Sb 2 is compared to that of the layered Zintl compounds A Zn2 Sb2 (A=Ca,Yb,Sr,Eu), which have smaller unit cells and larger lattice thermal conductivity, κL ∼2 W m-1 K-1, at 300 K. Ultrasonic measurements, in combination with kinetic theory and the estimated κL values, suggest that the lower κL of SrZn Sb2 is primarily the result of a reduction in the volumetric specific heat of the acoustic phonons due to the increased number of atoms per unit cell. Therefore, this work recommends that unit cell size should be considered when selecting Zintl compounds for potential thermoelectric application. © 2009 American Institute of Physics.