Influence of nanowires and nanotubes on the thermal conductivity of graphene-Bi2Te3 based nanostructured materials

The development of highly efficient thermoelectric materials with higher energy conversion efficiency is the main challenge currently due to the interdependence of electrical conductivity and thermal conductivity of the thermoelectric materials. Though some progress has been already established to improve the electrical conductivity of thermoelectric materials, most of the reported thermoelectric materials exhibit very high thermal conductivity. In this present work, an attempt has been made to improve the energy conversion efficiency of thermoelectric materials by lowering the thermal conductivity. For this purpose, different morphologies of the starting bismuth telluride (Bi2Te3) nanomaterial (nanowires and nanotubes) have been utilized as host materials to fabricate the graphene oxide(GO)- and reduced graphene oxide(rGO)-based nanocomposites by using a mechanical alloying process. A cold-pressed method has been utilized to prepare the nanostructured rGO/GO-bismuth telluride samples to retain the initial morphology of the host nanomaterials. Our experimental results revealed that the larger diameter bismuth telluride nanomaterials-based nanostructured materials showed a higher Seebeck coefficient and lower thermal conductivity (0.26 W/m-K) as compared to the smaller diameter and nanowires-based bismuth telluride thermoelectric materials. The underlying mechanism for such improvement in the Seebeck coefficient and thermal conductivity has also been reported.