Etude de l'insertion dans le graphite des alliages binaires KBi, RbBi, et CsBi

Abstract

A systematic study of the intercalation into graphite of the binary alloys KBi, RbBi, and CsBi has been realized. These various alloys intercalate easily, provided that their compositions are appropriately selected. Tables 1, 3, and 5 collect the ternary compounds that have been observed, respectively, in the case of potassium, rubidium, and cesium. In these tables, the compounds that are not isolated are pointed out by an asterisk. The bismuthographitides of potassium (Table 1) present a stage varying between 2 and 5; they are of two different types, α and β, characterized by interplanar distances of 9.90 Å and 10.86 Å, respectively. The chemical analysis (Table 2) leads to the formulae KBi 0.6C 8 and KBi 0.6C 12 for the a ternary compounds of stages 2 and 3. With rubidium (Table 3), it appears also two different varieties, α and β, whose interplanar distances are, respectively, 10.10 Å and 10.52 Å. The stage can vary in this case between 1 and 7. The chemical formulae (Table 4) are close to RbBi 0.6 C 4 and RbBi 0.6C 8 for the a compounds of stages 1 and 2. Finally, the compounds of cesium (Table 5) present interplanar distances of 10.70 Å and 11.50 Å, respectively, for the α and β varieties. Their stage varies between 1 and 4. The product of the reaction on the graphite of the binary alkali metal-bismuth alloy depends strongly of the composition of this alloy. Figures 1, 2, and 3 show the effect of this factor on the reaction product, successively for the potassium, rubidium and cesium alloys. The upper part of these figures gives the liquid-solid phase diagram of the studied alloys. The lower one indicates the various products, which are obtained by action on the graphite of the corresponding liquid alloys. In each case, the whole range of concentration is subdivided into various intervals corresponding to the domains of existence of the various compounds or mixtures of compounds indicated. The ternary phases appear only in the intermediate range of composition. Indeed, an alloy too rich in alkali metal leads only to binary compounds, and an alloy too rich in bismuth does not react with graphite at all.