Thermoelectric Properties and Electrical Transport of Graphite Intercalation Compounds

Abstract

Graphite intercalation compounds (GICs) have high electrical conductivities, large Seebeck coefficients, and low thermal conductivities as compared with their host graphite materials. Due to these properties, GICs are expected to act as effective thermoelectric materials. The thermoelectric figure of merit of the GICs is not as high as that of other thermoelectric materials; this is because of the small Seebeck coefficient and high thermal conductivity of GICs. However, the thermoelectric power factor of GICs is sufficiently high at present. In previous works, it was suggested that an increase in concentration of the intercalated species improves the thermoelectric performance of GICs. To better understand the thermoelectric properties of GICs, the dependence of thermoelectric properties with the electrical carrier density and mobility were investigated through the measurements of galvanomagnetic properties. As a result, the electrical conductivity of GICs slightly increases with the carrier density and the thermal conductivity increases with the carrier mobility. Furthermore, the carrier mobility decreases with an increase in the carrier density. In conclusion, the thermoelectric performance of GICs is suggested to be improved by an increase in the carrier density, that is, by an increase in the intercalate concentration.