Glassy thermal conductivity in the two-phase CuxAg3-xSbSeTe2 alloy and high temperature thermoelectric behavior

We have measured the thermal transport properties over the temperature range 1.8 K<T<700 K of a two-phase alloy synthesized by reacting AgSbTe2 and Ag2Se in a 1:1 molar ratio. Typical electrical resistivity values at 700 K are in the range ∼4 mΩ cm≤ρ≤20 mΩ cm, while low thermal conductivity values (κ<1 W m-1 K-1) were obtained. We find that the thermal conductivity of this crystalline alloy has a temperature dependence strikingly similar to those of amorphous solids. In addition the thermal conductivity, thermopower, and electrical resistivity decouple. This result makes it possible to optimize thermoelectric performance by minimizing the electrical resistivity. It is therefore envisaged that this system has potential as a high performance bulk thermoelectric.