The electrical conductivity of graphite intercalated with superacid fluorides: experiments with antimony pentafluoride

Abstract

The electrical conductivity in graphite measured normal to the crystallographic c-axis is observed to increase after intercalation with acid molecules which act as acceptors. This behaviour is regarded as the result of ionization of the acid molecule which, in turn, increases the positive current carriers in the host graphite. Since the carrier density depends on the degree of ionization of the acid, it follows that the stronger the acid the greater the increase in carrier concentration, and assuming no adverse mobility effects, the greater the electrical conductivity. The hydrogen fluoride-antimony pentafluoride system produces some of the strongest acid substances known. The experiments described here represent the initial examination of the electrical conductivity resulting from intercalation of this material into graphite. The experiments consisted of intercalating graphite powder with antimony pentafluoride in a copper tube and swaging the sheathed compound into wire. The measured conductivity of the graphite intercalation compound, when the copper conductivity is subtracted out and allowance is made for departure from ideal density, is about 1×10⁶ Ω⁻¹ cm⁻¹. This is approximately 40 times the conductivity of pristine graphite and more than one and a half times the conductivity of pure copper.