Small Seebeck coefficient of graphite intercalation compounds containing CaC6

Calcium graphite intercalation compounds (Ca-GICs; the composition is CaC6) and GICs containing CaC6 are synthesized from Grafoil and PGS graphite sheets, and the Seebeck coefficients are measured. The absolute values of the Seebeck coefficient of these GICs are very small; in some cases, the values are positive. This phenomenon observed in the Seebeck coefficient of GICs containing CaC6 is very different from that of general GICs such as alkali-metal GICs. The temperature dependence of the Seebeck coefficient of these GICs is to that of general GICs; that is, the absolute values of the Seebeck coefficient decrease with a decrease in the temperature.