The lattice dynamics in the IV-VI compounds GeTe, SnTe and PbTe were studied by 125 Te and 119 Sn nuclear inelastic scattering and the obtained partial density of phonon states were compared with published theoretical calculations. The phase purity and structure were characterized by high energy X-ray diffraction. The effect of the atomic arrangement, rhombo-hedral for GeTe and cubic for SnTe and PbTe, is visible in the density of phonon states. Vibrational properties are found to be in good agreement with available calculated data and the softer character of the NaCl-type structures in comparison with the rhombohedral GeTe is confirmed.

An alloy engineering approach aiming to produce a fine two-phase mixture thermoelectric material is highlighted in order to reduce the thermal diffusivity. We utilized the spinodal decomposition in the PbTe-GeTe quasi-binary system to control the alloy microstructure through solutioning, quenching and aging treatments. The effect of various microstructural states on the thermal diffusivity is analyzed. It is observed that a minimum in thermal diffusivity is obtained when several microstructural contributions are combined.