Structural and thermoelectric properties of AgSbTe₂-AgSbSe₂ pseudobinary system

Structural properties of the AgSbTe₂-AgSbSe₂ pseudobinary system were examined using thermal analysis, scanning electron microscopy, and x-ray powder diffractometry. It was found that partial substitution of Te by Se atoms leads to stabilization of the cubic crystal structure of alloys. The electronic-transport properties of materials were measured in order to investigate carrier conduction, band-gap features, and thermoelectric properties. The undoped homogeneous solid solution exhibits extremely low thermal conductivity of 0.5 W m⁻¹ K⁻¹, a very large positive Seebeck coefficient of about 400–600 μV K⁻¹ at room temperature, low carrier densities of 10¹⁶–10¹⁸ cm⁻³, and thermally activated conduction. The influence of alloying on thermal-conductivity mechanisms and electron properties was discussed. The highest experimental dimensionless figure of merit ZT of the undoped AgSbSe_0.25Te_1.75 sample is about 0.65 at a temperature of 520 K. The influence of doping on enhancement of thermoelectric properties of these materials was analyzed and optimal values of transport parameters were estimated.