Thermoelectric properties of Bi0.5Sb1.5Te3/Ag2Te bulk composites with size- and shape-controlled Ag2Te nano-particles dispersion

We investigated the particle size-dependent thermoelectric properties of conventional p-type Bi0.5Sb1.5Te3 compounds (L-large, M-medium, S-small sizes) and M-Bi0.5Sb1.5Te3/Ag2Te composites with commercial (C), nano-wire (NW), and nano-powder (NP) type Ag2Te nano materials. The sintered ingot with the medium size particles M-Bi0.5Sb1.5Te3 shows a high power factor of S2σ, due to its high electrical conductivity and Seebeck coefficient, with a maximum ZT (0.9 at 300 K). The S-Bi0.5Sb1.5Te3, synthesized by the wet-chemical method, exhibits the lowest thermal conductivity by grain boundary phonon scattering. The composites of M-Bi0.5Sb1.5Te3/Ag2Te show significantly enhanced electrical conductivities, as well as a decrease of lattice thermal conductivities, resulting in the enhancement of ZT (1.1 at 575 K) for a NP-Ag2Te dispersed M-Bi0.5Sb1.5Te3/NP-Ag2Te composite. Here, we propose that the Bi0.5Sb1.5Te3/Ag2Te composite can be employed as a material for waste heat power generation.