Improved thermoelectric properties of AgSbTe2 based compounds with nanoscale Ag2Te in situ precipitates

Ternary AgxSb2−xTe3−x thermoelectric materials have been prepared with x value varying from 0.78 to 0.93. By adjusting the Ag2Te ratio, double-phased in situ nanocomposites were obtained with the nanostructured Ag2Te embedded in the AgSbTe2 matrix when x > 0.81. The high-resolution transmission electron microscopy observation showed that the Ag2Te precipitates were in situ formed as nanodots and nanoscale lamellar structures. Compared with the single-phased samples of x = 0.78 and 0.81, the Seebeck coefficient of the nanocomposite samples exhibited significant improvement over the entire measured temperature range and the electrical conductivity also slightly increased, resulting in the increase of the power factor. At the same time, the thermal conductivity of the nanocomposite samples slightly decreased. The optimization of both the power factor and the thermal conductivity contributed to the notable improvement in figure of merit ZT by a factor of ∼40% at 670 K.