Synthesis and thermoelectric properties of the PbSe1−xTex alloys

The PbSe1−xTex alloys with x = 0.2, 0.3, 0.5, 0.85 and 1.0 were prepared by induction melting, ball milling and spark plasma sintering techniques. The thermoelectric properties of the samples were investigated. The XRD analysis indicated that all samples are NaCl-type structure solid solutions Pb(Se,Te) containing nanograins. Increasing Te content resulted in increasing the lattice parameter a. The thermoelectric measurements show that all samples are n-type semiconductors in temperature range from 300 K to 673 K. The electrical resistivity of the doped sample is much smaller than that of pure PbSe, but comparable to that of PbTe. The absolute Seebeck coefficients for the doped sample PbSe1−xTex with x = 0.2, 0.3 and 0.5 range from 150 μV/K at 300 K to 250 μV/K at 673 K, which is much larger than that of pure PbSe (66–138 μV/K), but smaller than that of PbTe (230–310 μV/K) in the same experimental conditions. The thermal conductivity for the doped sample PbSe1−xTex with x = 0.2, 0.3 and 0.5 range from 0.95 to 0.66 W/m K, which is much smaller than that of pure PbSe (2.1–1.3 W/m K) or PbTe (1.4–1.1 W/m K). As a result, the figure of merit for the doped sample can be enhanced. The maximum dimensionless figure of merit ZT of 1.15 was obtained in the sample PbTe0.5Se0.5 at 573 K, more than 50% higher than that of pure PbTe prepared in the same condition.

Research highlights
► The n-type semiconductor solid solutions PbTexSe1−x containing nanograins were prepared.
► Low electrical resistivities were found in the solid solutions PbTexSe1−x due to the modification of the interface between the grains.
► The very low thermal conductivities were attained in the solid solutions PbTexSe1−x due to the nanograins and atomic disorder.
► The maximum dimensionless figure of merit ZT of 1.15 was obtained in the sample PbTe0.5Se0.5 at 573 K.