Influence of Ag and Cu Doping on the Structure and Thermoelectric Properties of Β-Zn8Sb7 Thin Film

Abstract

The low lattice thermal conductivity of the intermetallic compound Zn8Sb7 makes it an intriguing thermoelectric material. We determined the structural characteristics and identified the increasingly anharmonic behavior of the Zn atoms for both undoped and doped Zn8Sb7 with 5% Cu, Ag, or a mixture of them by utilizing X-ray diffraction and Rietveld refinement. The doped Zn8Sb7 thin films exhibit superior thermoelectric performance compared to the undoped ones and were deposited using direct current magnetron co-evaporation. The study validates a significant enhancement of the thermoelectric figure-of-merit (ZT) following Cu doping, yielding ZT values of about 1.642 at 600 K. This enhancement results from a notable reduction in resistivity, which is linked to a two-fold increase in the concentration of hole charge carriers. It has been suggested that small amounts of Zn in the crystal structure can be replaced with Cu or Ag, which would strengthen Zn8Sb7's intrinsic impurity band.