Intriguing metal–semiconductor transport properties on Se-substituted β-Zn4Sb3 compounds

Among the numerous thermoelectric compounds, β-Zn 4 Sb 3 has gained significant interest as a promising thermoelectric material due to its effective working temperature range and enhanced figure of merit (ZT) values. In this work, the effect of Se doping in β-Zn 4 Sb 3 system has been studied. The structure refinement of the prepared Zn 3.9 Se 0.1 Sb 3 solid solution was carried out using Rietveld refinement analysis, which confirms that the compound crystallizes in hexagonal rhombohedric structure with R-3c space group. Temperature-dependent electrical conductivity ( σ ) of the sample has been measured in the temperature range of 300–610 K. At room temperature, the electrical conductivity value of the sample was found to be high (~1919 S m −1 ) and it tends to decrease upon increasing the temperature up to 514 K and thereafter slightly increases, which indicates the typical metallic to semiconductor transition behaviour of the prepared compound. The positive Hall coefficient ( R H ) value reveals that the holes are the dominant charge carriers (p-type) in the prepared sample. The power factor value ( σS 2 ) of the sample increases linearly with increase in temperature up to 610 K. Hence the Se substitution in pristine Zn 4 Sb 3 possesses greater effect in inducing superior thermoelectric power factor values. Temperature-dependent total thermal conductivity ( κ total ) of Zn 3.9 Se 0.1 Sb 3 sample is measured in the temperature range of 300 to 610 K. At room temperature, the κ total value of the sample was found to be very low (~1 Wm −1 K −1 ) and it decreases linearly with increasing the temperature. At 610 K, the sample shows merely ultra-low-thermal conductivity value (~0.6 Wm −1 K −1 ). A peak ZT value of ~0.3 was obtained in Zn 3.9 Se 0.1 Sb 3 solid solution at 610 K, which was found to be quite competitive with the current thermoelectric materials.