Electron Diffraction study of Layer Structures in La-Mg-Ni Hydrogen Absorption Alloys

Abstract

In order to improve the hydrogen absorption properties of the layer structure appearing at the nickel rich side of La-Mg-Ni alloy, appropriate amounts of Ni were replaced by some elemental atoms, Mn, Co and Al. The La_0.8Mg_0.2Ni_3.4−xCo_0.3(MnAl)_x (0<x<0.4) alloy system was synthesized and crystal structures were investigated by electron microscopy. The atomic concentration ratio of (LaMg) to the other atoms was 3.7 in this system. The Pr₅Co₁₉-type structure (5:19H-structure) and the Ce₅Co₁₉-type structure (5:19R-structure) were found in this alloy system. Electron micrographs of these structures are presented in this paper. Structure analysis of the complex layer structure is demonstrated by careful observation of the electron diffraction pattern.