Ionic salt limit in graphite--fluoroarsenate intercalation compounds

Starting with C/sub 8n/AsF5 intercalation compounds of stage n = 1 and 2, we have recorded changes with fluorine uptake in basal plane conductivity and its temperature variation, reflectivity and C(1s) core level x-ray photoemission spectra. The data are all consistent with an ionic salt limit C+20 (0.05 electrons per C atom extracted by oxidation) beyond which direct fluorination takes place. Defect scattering from the resulting C--F bond sites is shown to be the conductivity-limiting factor, rather than π charge localization around AsF6- sites. The present results also support our previous conclusions that the oxidation of the initial compounds by AsF5 goes only 40% and 52% to completion for stages 1 and 2, respectively