Contribution of Embedded Bromine Molecules to the Dielectric Properties of Fluorinated Graphite Intercalation Compounds

Here, we study the dielectric properties of fluorinated graphites C2Fx with different fluorine contents (x approximate to 1.05, 0.85, and 0.60) and embedded bromine molecules by impedance spectroscopy. An analysis of the results using the Maxwell-Garnett approximation made it possible to estimate the contributions of the fluorinated graphite matrix and bromine guests to the dielectric permittivity of the compound. The permittivity of the C2Fx matrix increases with decreasing fluorine content and does not depend on temperature. The change in the permittivity upon cooling/heating of the samples is provided by the polarization of bromine molecules Br2. The significant temperature-dependent dielectric response of C2F0.60 is associated with the formation of bromine and polybromide ions, such as Br2- and Br3-, in the interlayer space of the matrix. The decrease in the permittivity at low temperature is explained by the freezing of the ion mobility.

Automated summary

The dielectric properties of fluorinated graphites with different fluorine contents and embedded bromine molecules were studied by impedance spectroscopy. The contributions of the fluorinated graphite matrix and bromine guests to the dielectric permittivity were estimated using the Maxwell-Garnett approximation. The permittivity of the fluorinated graphite matrix increased with decreasing fluorine content and was not temperature-dependent. The change in permittivity upon cooling/heating was caused by the polarization of bromine molecules. The temperature-dependent dielectric response of fluorinated graphite with a fluorine content of 0.60 was attributed to the formation of bromine and polybromide ions in the interlayer space, with a decrease in permittivity at low temperatures due to the freezing of ion mobility.