121Sb Moessbauer spectroscopic investigations of graphite intercalation compounds of the Cn · SbCl5 · MCl3 type (M = Al, Fe, Sb, As)

Using 121Sb Moessbauer spectroscopy information concerning both ionicity and valence state of intercalated species in ternary graphite intercalation compounds (GIC) can be obtained. It was found that the major portion of antimony in SbCl5/MCl3-GICs has the valence state of Sb(V), and that oxidation of graphite takes place only to a certain extent. Two different antimony phases, a neutral and a negatively charged species, were shown to exist by evaluation of the spectra in the Sb(V) region. In comparison with the binary SbCl5-GIC the changes of the isomer shift may be a consequence of intermolecular interactions with the trichlorides. These changes are in accordance with Pauling's electronegativities. Assuming the existence of polymeric anions consisting of the species SbCl5, SbCl6- and MCl3 in the interlaminary spacings an interpretation of the spectra is given. For the ternary GIC the following structure is suggested Cn+(m SbCl5 · p MCl3 · q SbCl6)- with M = Al, Fe, Sb, and As. The trichlorides act as links between the Sb species. (author)