Improvement of the Mechanical Properties of Bi_0.5Sb_1.5Te₃/PTFE Composite Thermoelectric Material

Abstract

We have fabricated nanocomposite ceramics of Bi_0.5Sb_1.5Te₃/PTFE （Poly-Tetra-Fluoro-Ethylene） to improve the mechanical properties of the state-of-the-art thermoelectric Bi_0.5Sb_1.5Te₃. The Bi_0.5Sb_1.5Te₃/PTFE ceramics were prepared by sintering mixed powders of micrometer size Bi_0.5Sb_1.5Te₃ and nanometer size PTFE. While the addition of excess amount of PTFE particles to the Bi_0.5Sb_1.5Te₃ matrix lead to deterioration of the thermoelectric performance by significant increase in electrical resistivity over the decrease in thermal conductivity, we found that addition of small amount （around 0.5 mass％） can lead to improvement of the mechanical strength up to 22％ of the original value without deteriorating the thermoelectric performance. Microstructural analysis revealed the presence of a void structure around the PTFE particles. We assume that the plasticity of PTFE is responsible for the improvement of the mechanical strength while both PTFE and the voids are responsible for the reduction in thermal conductivity.