The peak zT value of 1.1 has achieved for Pb0.995Sb0.005Te alloy at 723 K, which is comparable with the Sb doped PbTe alloys with higher doping concentration.

The quaternary chalcogenide composites Cu 2 ZnSn 1−x Ag x Se 4 (0 ≤ x ≤ 0.075) have been successfully synthesized by high-temperature melting and annealing followed by hot-pressing. The phase structure of the bulk sample has been analyzed by powder X-ray diffraction and Rietveld refinement combined with Raman spectroscopy to confirm Cu 2 ZnSnSe 4 as the main phase with ZnSe and Cu 5 Zn 8 secondary phases. The thermoelectric properties of all specimens have been investigated in the temperature range of 300−700 K. The replacement of Sn by Ag significantly enhances the electrical transport properties by providing extra charge carriers. The tremendous reduction in electrical resistivity enhances the power factor, and a maximum power factor of 804 μW K −2 m −1 is achieved at 673 K for the specimen with 5% Ag content. Furthermore, increased point defects increase phonon scattering, resulting in reduced thermal conductivity. The combined effect of improved power factor and suppressed thermal conductivity provides a good boost to the dimensionless figure of merit. The maximum figure of merit of zT = 0.25 has been achieved at 673 K for Cu 2 ZnSn 0.95 Ag 0.05 Se 4 , which is 2.5 times the value of the parent sample.

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High zTs of Pb1−xBixTe alloys rapidly synthesized at low temperature in this study are comparable to those from conventional melting synthesis.