Thermoelectric Properties of Cesium–Graphite Intercalation Compounds

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The thermoelectric properties of cesium–graphite intercalation compounds (Cs-GICs) and some other GICs were studied. The electrical conductivities of the Cs-GICs prepared from Grafoil were around 10⁶ Ω⁻¹ m⁻¹, about 10 times higher than that of the host graphite, and the thermal conductivities were 50–100 Wm⁻¹ K⁻¹, about 1/4–1/2 of that of the host graphite. While the Seebeck coefficient of the host graphite was nearly zero, those of the Cs-GICs were found to be around −30 μV K⁻¹. These properties were determined also for the Cs-GICs prepared from well-oriented PGS graphite sheets. Consequently, the figures of merit of the Cs-GICs were of the order of 10⁻⁵ K⁻¹, approximately 10⁵ times higher than that of the host graphite. The power factor of the Cs-GICs reached the order of 10⁻³ Wm⁻¹ K⁻², with the best datum at 6.5×10⁻³ Wm⁻¹ K⁻². The carrier density of the GICs increased as the concentration of intercalated species increased, whereas their lattice thermal conductivities decreased. It is suggested that highly concentrated GICs might be promising candidate thermoelectric materials.