Role of graphite on the thermoelectric performance of Sb2Te3/graphite nanocomposite

Abstract

Thermoelectric properties of nanostructured Sb2Te3/graphite composites are investigated both experimentally and theoretically and the contribution of graphite to heat transport mechanism is addressed. XRD results indicate the solid state insolubility of the graphite phase in Sb2Te3 as no shift is observed in the diffraction peaks corresponding to Sb2Te3 in the composite samples. Raman spectroscopic analysis confirms the presence of graphite in the nanostructured composite samples. Temperature dependence of carrier concentration nH, thermal conductivity κ, Seebeck coefficient S, resistivity ρ, and, hence, the thermoelectric figure of merit ZT is reported. Graphite incorporation leads to around 40% decrease of κ, essentially due to the decrease of lattice thermal conductivity, κL. A low κL value of 0.8 Wm−1 K−1 is reported, which mostly arises due to enhanced phonon scattering at the heterointerfaces created by the addition of graphite. S increases in Sb2Te3/graphite nanocomposites. Calculation reveals that reported large S value is related with the low hole concentration. Theoretical simulation in the frame of Boltzmann equation approach shows satisfactory agreement of nH, S, and ρ with experimental data, and based on the modification of the density of states and its derivative near Fermi energy with graphite addition, a plausible explanation is provided.