Structure of LaNi<sub>3.8</sub>AlMn<sub>0.2</sub> Compounds Studied by Neutron Powder Diffraction

Abstract

The structures of as-cast LaNi3.8AlMn0.2 alloys and subsequent compounds by means of annealing at different temperature (850, 900, 950, 1000 oC) were examined by using neutron powder diffraction (NPD) and X-ray diffraction (XRD). Based on the Rietveld method, the diffraction data was refined using FullProf software. The refined results demonstrate the structure types of all compounds are CaCu5 type and their space groups are P6/mmm. Increasing the annealing temperature, the lattice parameters of LaNi3.8AlMn0.2 compounds did not possess clearly linear variation. It is noted that Mn atoms do not occupy the 2c sites but occupy the 3g sites in all compounds.