Versatile behavior upon intercalation by chemical vapor transport of lanthanide trichlorides into graphite

Lanthanide trichlorides which hardly react with graphite have been moved into the latter by chemical vapor transport (CVT) thanks to a gaseous complex LnAl3Cl12 resulting from the reaction between LnCl3 and AlCl3. This complex molecule also allows the intercalation of LnCl3 into graphite, AlCl3 playing the role of a gaseous medium and/or co-intercalated species, depending on the structure of the pristine chloride. Well-defined stage-2 to 4 graphite intercalation compounds (GICs) have been synthesized by this CVT method, but efforts to get richer stage-1 compounds are still in progress. The 0 0 l structural study of stage-2 GICs performed by XRD reveals that interplanar distances of LnCl3-GICs are higher than those classically observed for intercalated transition metal chlorides. The composition of all the stage-2 compounds studied has been established and ternary C-LnCl3–AlCl3 compounds with a significant excess of chlorine have been observed. The 2D structures of the different LnCl3-GICs have been characterized by X-ray or electron diffraction and show that structural differences are noted between pristine and intercalated LnCl3.