POTASSIUM OXYGEN GRAPHITE-INTERCALATION COMPOUNDS

Intercalation of potassium superoxide KO2 into graphite in the presence of potassium metal was studied. Graphite intercalation compounds of stage 1 (assigned formula C4KO2, c-axis repeat distance 8.44 Angstrom) and stage 2 (assigned formula C8KO2, c-axis repeat distance 11.75 Angstrom) were synthesized and isolated for the first time. A quadruple intercalate layer K-O-O-K is supposed. In-plane structure of the intercalate layer is discussed mostly on the basis of X-ray diffraction intensity analysis and transmission electron microscopy electron diffraction. A metal-like temperature dependence of c-axis resistivity was obtained in the 1.5-300 K temperature range where the resistivity values at room temperature are 0.07 and 0.81 Ohm cm for stage-1 and stage-2 compounds, respectively. The results of magnetic susceptibility measurements suggest that the oxygen species are in nonmagnetic states.