Synergistic Optimization of Electrical–Thermal–Mechanical Properties of the In-Filled CoSb₃ Material by Introducing Bi_0.5Sb_1.5Te₃ Nanoparticles

How to realize the synergistic optimization of electrical–thermal–mechanical properties of thermoelectric materials is a key challenge. Using the Bi0.5Sb1.5Te3 nanoparticle as a mixed agent provides an effective way to address this challenge. Here, Bi0.5Sb1.5Te3/In0.25Co4Sb12 nanocomposites with different contents of Bi0.5Sb1.5Te3 nanoparticles were successfully prepared by ultrasonic dispersion combined with spark plasma sintering. Phase and microstructure characterization presented that Te nanoparticles were precipitated from Bi0.5Sb1.5Te3 during the SPS sintering process. Transport measurement results showed that the electrical conductivity was increased due to the increased carrier concentration induced by the charge transfer between Te nanoparticles and the matrix. The Seebeck coefficient was also increased due to the selected electron scattering and increased scattering factor. The lattice thermal conductivity was dramatically suppressed because of the enhanced phonon scattering induced by the Bi0.5Sb1.5Te3 nanoparticles and in situ-precipitated Te nanoparticles and increased dislocations. As a result, a higher average ZT value of 1 was obtained in the range of 300–700 K by the decoupling of the electrical and thermal transport properties for the nanocomposite with 0.1 wt % of Bi0.5Sb1.5Te3 nanometer suspension. Furthermore, the flexural strength, fracture toughness, and hardness of the nanocomposites were also improved significantly. This work demonstrates that using the Bi0.5Sb1.5Te3 nanoparticle as a mixed agent can realize the synergistic optimization of electrical–thermal–mechanical properties of the In-filled CoSb3 thermoelectric material.