Structure and Electronic Properties of La(Ni,Al)5 Alloys

Nanocrystalline and polycrystalline La(Ni,Al)₅ alloys were prepared by mechanical alloying (MA) followed by annealing and arc melting method, respectively. The amorphous phase of MA samples forms directly from the starting mixture of the elements, without other phase formation. Heating the MA powders at 800 °C for 1 h resulted in the creation of hexagonal CaCu₅‐type nanocrystalline compound with mean crystallite size less than 80 nm. XPS studies showed that the shape of the valence band measured for the arc melted (polycrystalline) LaNi₅ is practically the same compared to that reported earlier for the single crystalline sample. The substitution of Ni in LaNi₅ by Al leads to significant modifications of the electronic structure of the polycrystalline sample. On the other hand, the XPS valence band of the MA nanocrystalline LaNi_4.2Al_0.8 alloy is considerably broader compared to that measured for the polycrystalline sample. The strong modifications of the electronic structure of the nanocrystalline LaNi_4.2Al_0.8 alloy could significantly influence on its hydrogenation properties.