Nuclear microanalysis: An efficient tool to study intercalation compounds containing lithium

Lithium can intercalate easily into graphite leading to the LiC 6 compound but the synthesis of a ternary compound associating lithium with a second element seems to be difficult. Recently, graphite–lithium–calcium compounds were obtained by reaction of a pyrographite platelet in a molten Ca–Li alloy at 350 °C. Chemical analyses, electron microprobe, SEM and TEM give the C/Ca ratio but do not allow to determine the lithium concentration and its distribution in these compounds. Therefore, the nuclear microprobe was used to characterise more precisely these ternary intercalation compounds. Using a 3.1 MeV proton beam, the three elements can be quantified simultaneously from the 7 Li(p,α) 4 He nuclear reaction for lithium and from elastic scattering for calcium and carbon. Among the three synthesised compounds, one of them (α phase) opposes great heterogeneities in lithium and the amount of lithium in the β phase is very high (C/Li ratio approaches 2).