Electrical properties of room temperature fluorine-intercalated graphite fibers

Abstract

Fluorine-intercalated graphite fibers have been synthesized at room temperature by direct reaction with elemental fluorine. The host materials were either vapor-grown fibers or pitch-based fibers. The C x F compounds obtained were mostly of the stage-3 type with a 12.65 Å repeat distance. The carbon-to-fluorine atomic ratio ranged from 10 to 14. Resistivity measurements carried out between 4.2 and 300 K show clearly that the fluorination reduces the resistivity values, whatever the type of pristine material. For fluorine-intercalated pitch-based fibers an anomalous increase of resistivity below 30 K may be consistent with a weak electronic localization or with two-dimensional carrier-carrier interaction effects. In fluorine-intercalated vapor-grown fibers the anomalous bump observed around 190 K could result from a phase transition. The room temperature value of the conductivity of this type of material, i.e. σ = 1.6 × 10 5 S cm −1, is one of the highest ever observed for fluorine-intercalated C x F fibers.