Thermoelectric and microstructural properties of Pb0.9−xSn0.1GexTe compounds prepared by spinodal decomposition

Three samples of Pb_0.9−xSn_0.1Ge_xTe with x=0.25, 0.35, 0.6 were prepared by heating the mixtures above the melting point of the constituent elements followed by quenching in water. The x=0.6 sample is close to the center of the immiscibility region, while the x=0.25 and 0.35 samples are in the Pb rich region inside the spinodal miscibility gap. Microstructural investigations using Powder X-ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy revealed both GeTe-rich and PbTe-rich phases. The samples were uniaxially hot pressed and the thermoelectric properties were characterized in the temperature range 2-400 K using a commercial apparatus and from 300 to 650 K with a custom designed setup. The best sample (x=0.6) reached zT≈0.6 at 650 K, while the x=0.25 and 0.35 samples showed thermal instability at elevated temperatures.