Preparation And Properties Of PbTe Based Bulk Thermoelectric Materials

Thermoelectric materials are a kind of functional semiconductors that can directly convert electrical power to heat or conversely, with the merit of reliability and noiseless etc. Particularly, the Ag and/or Sb doped PbTe thermoelectric bulk materials have the advantage of low-cost preparation process and reasonable thermoelectric properties, so as to attract much attention in research. Doped PbTeSe based materials and GeTe-PbTe based materials were produced and investigated.Pb9.6Sb0.2Te10-xSexand Pb9.6SbxTe3Se7 alloys have been produced by slow cooling in evacuated tubes and the effects of Sb substitution on the Pb site on the thermoelectric properties were investigated. It is noteworthy that Pb9.6Sb0.3Te3Se7 exhibit a high thermoelectric figure of merit, with the highest ZT～1.14 at 673 K. This value is about 50% higher than that of the state-of-the-art PbTe-based alloys reported previously. High resolution transmission electron microscopy studies suggest the Pb9.6Sb0.3Te3Se7 phases are inhomogeneous at the nanoscale with widely distributed nanosized islands of varying sizes and shapes, which are favorable to the strong suppression of the lattice conductivity. AgxPb9.6Sb0.2Te2+x/2Se8 were synthesized to study the effect of Ag substitution on the Pb site on the thermoelectric properties. The widely distributed microfractures in the samples lead to low electrical conductivity, which is responsible for the low figure of merit.The effects of preparation method on the thermoelectric property of Pb9.6Sbo.2Te3Se7 were studied. It has shown that the reduced lattice thermal conductivity of the samples subjected to less time of heat preservation cannot offset the reduced electrical conductivity, thus, slow cooling is more favorable to high figure of merit.PbTe-GeTe alloys were synthesized by liquid nitrogen quenching in evacuated tubes and SPS, due to complexity of fabrication method, the alloys exhibit a low Seebeck coefficient and a low thermoelectric figure of merit.