The influence of co-doping Ag and Sb on microstructure and thermoelectric properties of PbTe prepared by combining hydrothermal synthesis and melting

Ag and Sb co-doped PbTe (AgPb18SbTe20) and pure PbTe nanopowders were hydrothermally synthesized. The synthesized nanopowders were heated at 1173–1223 K in vacuum for 5 h followed by a slow cooling. The nanopowders and the bulk samples were characterized by X-ray diffraction and electron microscopy, respectively. Electrical transport properties of the bulk samples were measured from room temperature to ∼773 K. The results showed that co-doping Ag and Sb into PbTe has significant effects on both the nanopowders and bulk samples. Bulk AgPb18SbTe20 sample showed n-type conduction in the whole temperature range measured, while bulk PbTe sample exhibited a transition from p- to n-type conduction at ∼500 K. The thermoelectric properties of PbTe were markedly improved after co-doping of Ag and Sb. The AgPb18SbTe20 sample has a dimensionless figure of merit of ∼0.94 at 723 K.