Enhanced Thermoelectric Performance in the Ba0.3Co₄Sb₁₂/InSb Nanocomposite Originating from the Minimum Possible Lattice Thermal Conductivity

The thermoelectric efficiency of skutterudite materials can be improved by lowering the lattice thermal conductivity via the uniform dispersion of a nanosized second phase in the matrix of filled Co 4 Sb 12 . In this work, nanocomposites of Ba 0.3 Co 4 Sb 12 and InSb were synthesized using ball-milling and spark plasma sintering. The thermoelectric transport properties were studied from 4.2 to 773 K. The InSb nanoparticles of ∼20 nm were found to be dispersed in the Ba 0.3 Co 4 Sb 12 grains with a few larger grains of about 10 μm due to the agglomeration of the InSb nanoparticles. The +2 oxidation state of Ba in Co 4 Sb 12 resulted in a low electrical resistivity, ρ, value of the matrix. The enhancement of the Seebeck coefficient, S, and the electrical resistivity values of Ba 0.3 Co 4 Sb 12 with the addition of InSb can be credited to the energy-filtering effect of electrons with low energy at the interfaces. The power factor of the composites could not be enhanced compared to the matrix because of the very high ρ value. A minimum possible lattice thermal conductivity (0.45 W/m·K at 773 K) was achieved due to the combined effect of rattling of Ba atoms in the voids and enhanced phonon scattering at the interfaces induced by nanosized InSb particles. As a result, the (InSb) 0.15 + Ba 0.3 Co 4 Sb 12 composite exhibited improved thermoelectric properties with the highest zT of 1.4 at 773 K and improved mechanical properties with a higher hardness, higher Young’s modulus, and lower brittleness.