Structure formation and very low thermal conductivity in Pb:Te:Ag:Se mixtures

We have observed that reacting Pb:Te:Ag:Se in a 1:1:1.9:1 molar ratio gives rise to what appears to be a predominantly single-phase alloy, which crystallizes in the PbSe cF8 fcc structure. However, further investigation of the structure using energy dispersive x-ray analysis reveals the presence of two phases, PbSe and β-Ag2Te, with identical lattice parameters. The total thermal conductivity of the formed alloy is remarkably low for a crystalline material, κT<0.6W∕mK at 675K, it is reproducible, and in addition, the compound has good mechanical properties.