The Structural Studies of Phase Transitions in the Graphite Intercalation Compounds with Iodine Chloride and Bromine

Authors I.V. Ovsiienko , T.A. Len , O.I. Prokopov , M.O. Borovoy, L.Yu. Matzui , O.A. Syvolozhskyi

Taras Shevchenko National University of Kyiv, Physical Faculty, 64/13, Volodymyrska St., 01601 Kyiv, Ukraine

Issue Volume 11, Year 2019, Number 4
Dates Received 30 May 2019; revised manuscript received 01 August 2019; published online 22 August 2019
Citation I.V. Ovsiienko, T.A. Len, O.I. Prokopov, et al., J. Nano- Electron. Phys. 11 No 4, 04002 (2019)
PACS Number(s) 61.48.De, 00.00.Хх
Keywords Graphite intercalation compound, X-ray diffraction method, Phase transition (6) , Intercalate layer.

The paper presents the results of investigation of phase transitions in the intercalation compounds based on fine crystalline anisotropic pyrolytic graphite with iodine chloride and bromine by X-ray diffraction method. As a source for intercalation, the fine crystalline pyrolytic anisotropic graphite with a distance between neighboring graphite layers of 0.340 nm and a crystallite size of 20 nm was used. The intercalation reaction was carried out by standard two-temperature gas-phase method. The stability of graphite intercalation compounds under normal conditions is investigated. It is found that the exposure of graphite intercalation compound with iodine chloride under normal conditions during 20 days has not led to significant changes in the structure of compound while such exposure for graphite intercalation compound with bromine causes some changes in the structure. In particular, transition from the second stage compound to the third stage compound is observed. The coefficient of linear thermal expansion for graphite intercalation compounds with iodine chloride in different temperature intervals is estimated. It is revealed that at a temperature of 260 K there is a significant reduction of the value of the coefficient of linear temperature expansion. It is shown that such a sharp change of the coefficient of linear temperature expansion is related to the phase transition in the intercalate layers from quasicrystalline” state to “quasiliquid” state. For the first time, by the X-ray diffraction method the phase transition of the “disorder – order” type in the intercalate layers is found for graphite intercalation compounds with iodine chloride.

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