Fluorine-graphite HOPG intercalation compounds

Abstract Fluorine-graphite intercalation compounds C x F (15>×≥5.6) have been obtained by exposing HOPG to fluorine with available highest purity, at 50°C for periods exceeding 30 days. The identity period and the intercalant thickness of pure stage-2 compound C 6.4 F are, respectively, 9.46 and 2.76 A. In-plane electrical conductivities of C x F are ca. 8–10 times that of the pristine HOPG. The c-axis resistivity of the stage-2 compound vs. temperature shows a maximum at 194 K; metallic-like behavior at lower temperatures and semiconductor-like behavior at higher ones. The compound also shows an anomalous c-axis thermal expansion at 130 K and a drastic motional narrowing in the linewidth of 19 F-NMR at 150 K, suggesting a kind of in-plane phase transition of intercalated fluorine.