Transport properties of the layered Zintl compound SrZnSb2

Transport properties of the layered Zintl compound SrZnSb2 have been characterized from room temperature to 725K on polycrystalline samples. SrZnSb2 samples were found to be p-type with a Hall carrier concentration of 5×1020cm−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 SrZnSb2. A relatively low lattice thermal conductivity is observed, κL∼1.2Wm−1K−1, at room temperature. The thermal transport of SrZnSb2 is compared to that of the layered Zintl compounds AZn2Sb2 (A=Ca,Yb,Sr,Eu), which have smaller unit cells and larger lattice thermal conductivity, κL∼2Wm−1K−1, at 300K. Ultrasonic measurements, in combination with kinetic theory and the estimated κL values, suggest that the lower κL of SrZnSb2 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.