Insertion de lanthanoides dans le graphite
1980; Elsevier BV; Volume: 18; Issue: 3 Linguagem: Inglês
10.1016/0008-6223(80)90062-7
ISSN1873-3891
AutoresM. El Makrini, D. Guérard, Philippe Lagrange, A. Hérold,
Tópico(s)Advancements in Battery Materials
ResumoThe intercalation of lanthanides is possible by two different ways: direct action of the metal vapor in metallic tubes sealed under vacuum or by heating compressed mixture of powders of the metal and of graphite. The first method was used only for the most volatile metals: samarium, europium, thulium and ytterbium (see Table 1). The 00 l reflexions of the corresponding first stage graphitides MC6 (M = Sm, Eu, Tm or Yb) were obtained for samples prepared from pyrolytic graphite HOPG (Tables 2 and 3, Fig. 1). Using the second method, we determined the identity period along the c axis (Ic) for the most fusible lanthanides graphitides (Table 4). We did a study of the evolution vs temperature of a compressed mixture of initial composition Yb + 6C (Fig. 2). A structural study was carried out on single crystals of europium and ytterbium graphitides, using a special method developed in the laboratory. Figure 3 shows the three possible types of sites available to the metal atoms and the different stacking modes of the metallic layers. The hkO and hkl reflexions of the graphitide YbC6 (see Table 5) shown in Fig. 5 allow to choose between the three possible unit cells of Fig. 4. The hexagonal unit cells of EuC6 and YbC6 belong to the space group P63/mmc with two of three sites occupied regularly by the metal atoms. The two metal atoms are in position b and the twelve carbon atoms in i. The parameters are respectively a = 4.314 ± 0.003 Å, c = 9.745 ± 0.008 Å (EuC6) and a = 4.320 ± 0.004 Å, c = 9.147 ± 0.004 Å (YbC6).
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