TY - JOUR
T1 - Transmission electron microscopy study of order-disorder phenomena in non-stoichiometric LaNi5+x and LaNi6-xCux electrode materials
AU - Coene, W.M.J.M.
AU - Notten, P.H.L.
AU - Hakkens, F.
AU - Einerhand, R.E.F.
AU - Daams, J.L.C.
PY - 1992
Y1 - 1992
N2 - High-energy electron diffraction, X-ray powder diffraction and high-resolution electron microscopy have been used to investigate the crystallographic properties of non-stoichiometric LaNi5+x (0= =0.4) and LaNi6-xCux (0= =3.0) electrode materials, which are based on the CaCu5 structure type. Structural aspects with respect to Ni/Cu rich deviations from the exact AB5 stoichiometry are studied. X-ray powder diagrams show only the basic CaCu5 diffraction lines without any superstructure lines, and are therefore interpreted in terms of random substitutions of A atoms (La) by dumbbell pairs of B atoms (Ni/Cu) oriented along the c axis, thereby leading to a contraction and expansion of the lattice in the a and c direction, respectively. The observation of diffuse scattering in electron diffraction, which is located on a specific geometry in diffraction space, reveals that a large amount of the substitutions of A atoms by B2 dumbbells occur in a partially ordered manner. High-resolution electron microscopy shows that small Ni/Cu rich domains exist, in which the ordering is related to the stacking of A atoms and B2 dumbbells in the ordered rhombohedral and hexagonal A2B17 superstructures, and in the tetragonal AB12 superstructure.
AB - High-energy electron diffraction, X-ray powder diffraction and high-resolution electron microscopy have been used to investigate the crystallographic properties of non-stoichiometric LaNi5+x (0= =0.4) and LaNi6-xCux (0= =3.0) electrode materials, which are based on the CaCu5 structure type. Structural aspects with respect to Ni/Cu rich deviations from the exact AB5 stoichiometry are studied. X-ray powder diagrams show only the basic CaCu5 diffraction lines without any superstructure lines, and are therefore interpreted in terms of random substitutions of A atoms (La) by dumbbell pairs of B atoms (Ni/Cu) oriented along the c axis, thereby leading to a contraction and expansion of the lattice in the a and c direction, respectively. The observation of diffuse scattering in electron diffraction, which is located on a specific geometry in diffraction space, reveals that a large amount of the substitutions of A atoms by B2 dumbbells occur in a partially ordered manner. High-resolution electron microscopy shows that small Ni/Cu rich domains exist, in which the ordering is related to the stacking of A atoms and B2 dumbbells in the ordered rhombohedral and hexagonal A2B17 superstructures, and in the tetragonal AB12 superstructure.
U2 - 10.1080/01418619208205618
DO - 10.1080/01418619208205618
M3 - Article
VL - 65
SP - 1485
EP - 1502
JO - Philosophical Magazine A : physics of condensed matter, structure, defects and mechanical properties
JF - Philosophical Magazine A : physics of condensed matter, structure, defects and mechanical properties
SN - 0141-8610
IS - 6
ER -