High thermoelectric figure of merit and nanostructuring in bulk AgSbTe2

We report on thermoelectric properties of p-type AgSbTe2 bulk material with an in situ forming nanostructured Ag2Te phase that was prepared by combining a sonochemical method and spark plasma sintering. In order to control the density of nanodots, we synthesized samples with compositions (Ag2Te)x(Sb2Te3)100−x (x = 44∼54) and investigated their thermoelectric performance in the temperature range from 300 K to 600 K. Microstructure analysis shows that nanoparticles of Ag2Te with the size ranging from 10 nm to 50 nm are evenly embedded in the matrix. Transport measurements obtained on these samples demonstrate high power factors and low thermal conductivity and, consequently, an enhanced thermoelectric figure of merit ZT. Samples with compositions x = 48 and 50 reach power factors of ∼1.5 mW m−1 K−2 at about 400–500 K, while the thermal conductivity in this temperature range is about 0.6 W m−1 K−1. The best performance is obtained on a sample with x = 50 (AgSbTe2) where the ZT reaches 1.55 at 533 K, the value higher than for samples prepared by other methods over the same temperature range.