Phases and thermoelectric properties of Ge1−x(Pb0.9Yb0.1)xTe alloys

•A series of Ge1−x(Pb0.9Yb0.1)xTe alloys were prepared by SPS technique.•The alloys are composites containing the GeTe-based and PbTe-based phases.•The amount of the PbTe-based phase increases with x increasing.•The thermoelectric properties of the composites were systematically studied.•The maximum ZT of 1.4 at 723 K was found in the sample (Pb0.9Yb0.1Te)0.15(GeTe)0.85.

A series of Ge1−x(Pb0.9Yb0.1)xTe alloys with x = 0.05, 0.10, 0.15, 0.20 and 0.30 were prepared by a conventional melting and a spark plasma sintering (SPS) techniques. The phases and thermoelectric properties for the alloys were investigated. The alloys consist of the GeTe-based rhombohedral single phase for x = 0.05, while both GeTe-based rhombohedral and PbTe-based rock-salt phases due to spinodal decomposition for the higher Pb content (x ≥ 0.10). The amount of the PbTe-based phase increases with the Pb content x increasing. All samples show p-type conduction. As Pb content x increases, the thermal conductivity reduces obviously, while the Seebeck coefficient and the electrical resistivity increases slightly. The maximum ZT of 1.4 at 723 K was eventually achieved in the sample with x = 0.15 due to its rather low thermal conductivity, from 3.7 W m−1K−1 at room temperature to 1.4 W m−1K−1 at 723 K (3.7–1.4 W m−1K−1), relative high Seebeck coefficient (46.5–141 μV K−1) and relative low electrical resistivity (3.0–7.36 μΩ m).