Simultaneous increase in conductivity and phonon scattering in a graphene nanosheets/(Bi2Te3)0.2(Sb2Te3)0.8 thermoelectric nanocomposite

A thermoelectric nanocomposite of Bi0.4Sb1.6Te3 (BiSbTe) incorporated with the graphene nanosheets (GNs) has been synthesized and studied. The reduction of the carrier mobility is much less than the increase of the carrier concentration, resulting in the increase in conductivity at a low graphene nanosheets content. Simultaneously, graphene nanosheets causes 20-30% reduction in thermal conductivity (κ) owing to phonons blocking of nanosheets as well as phase boundaries. As a result, high dimensionless figure of merit (ZT) values of up to 1.29 (300 K) and 1.54 (440 K) are obtained in Bi0.4Sb1.6Te3 incorporated with only 0.3 vol.% and 0.4 vol.% graphene nanosheets, respectively, demonstrating that the thermoelectric performance of the BiSbTe alloy can be improved effectively through incorporation of GNs.