In situ synthesis and thermoelectric properties of PbTe–graphene nanocomposites by utilizing a facile and novel wet chemical method

In this work, a facile and novel wet chemical method is adopted to synthesize PbTe–graphene nanocomposites, and the thermoelectric properties of the sintered bulk materials are discussed in detail. An intercalative nanostructure is formed by using commercial graphene oxide nanosheets as both the dispersant and the two-dimensional growth template for PbTe nanoparticles in the synthesis process, where PbTe nanoparticles are in situ synthesized and graphene oxide nanosheets are reduced to graphene at the same time. FESEM and TEM measurements indicate that PbTe nanoparticles with sizes of 20–60 nm are uniformly anchored on the surface of graphene, and the nanostructure is retained in the bulk. These novel nanocomposites show enhanced thermoelectric properties as compared to bare PbTe prepared by the same route, as well as to samples prepared by traditional methods. The ultra-high electron mobility of graphene improves the electrical conductivity of the PbTe–graphene nanocomposites, and their conductivity exceeds not only that of bare PbTe but also the samples prepared by the traditional melt-quenching and melt-cooling processing techniques. Moreover, the much-decreased size of the PbTe particles in the bulk material, caused by the intercalative structure, increases the concentration of interfaces which results in the thermal conductivity of the nanocomposite being lower compared with the bare PbTe sample. Therefore, a much higher ZT value of the PbTe–graphene nanocomposites is obtained, reaching a value of 0.7 at 670 K. This is 6 times the value of the bare PbTe sample and a significantly higher ZT than for any n-type PbTe samples prepared by any of the traditional synthesis routes.