Enhanced thermoelectric properties of In-filled Co₄Sb₁₂ by dispersion of reduced graphene oxide

Uniform dispersion of nanosized secondary phases in bulk thermoelectric materials has proven to be an effective strategy to reduce the lattice part of thermal conductivity and improve the thermoelectric efficiency. In this work, reduced graphene oxide (rGO) was uniformly dispersed in the In_0.5Co₄Sb₁₂ bulk material by ultrasonication. The formation of impurity phases of InSb and CoSb₂ in the In-filled Co₄Sb₁₂ is inevitable, as observed from XRD and EPMA analyses. The Raman spectra of the nanocomposites showed broad peaks suggesting phonon softening and additional peaks corresponding to rGO. Electron transport was not affected by rGO addition, resulting in little change in the electrical resistivity and Seebeck coefficient. The lattice thermal conductivity of the bulk material was significantly reduced by the addition of a small amount of rGO, primarily attributed to the interface scattering of phonons. Hence, the highest zT of ∼1.53 at 773 K was achieved for the In_0.5Co₄Sb₁₂/0.25 vol% rGO composite in the temperature range from 723 K to 773 K.