Structural and thermoelectric properties ofAgSbTe2-AgSbSe2pseudobinary system

Abstract

Structural properties of the ${\text{AgSbTe}}_{2}{\text{-AgSbSe}}_{2}$ 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 $0.5\text{ }\text{W}\text{ }{\text{m}}^{\ensuremath{-}1}\text{ }{\text{K}}^{\ensuremath{-}1}$, a very large positive Seebeck coefficient of about $400--600\text{ }\ensuremath{\mu}\text{V}\text{ }{\text{K}}^{\ensuremath{-}1}$ at room temperature, low carrier densities of ${10}^{16}--{10}^{18}\text{ }{\text{cm}}^{\ensuremath{-}3}$, 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 ${\text{AgSbSe}}_{0.25}{\text{Te}}_{1.75}$ 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.