X-ray investigations of laves phase intermetallic compounds in the Gd 1−xEr xAl 2 system for 0 ⩽ x ⩽ 0.6

Abstract

The influence of the substitution of gadolinium atoms for erbium atoms in polycrystalline Gd 1− x Er x Al 2 Laves phase compounds was investigated. X-ray diffraction studies showed that all the samples crystallize with a cubic structure of the MgCu 2 type (C15). The lattice constants of the compounds satisfy Vegard's law for the whole range of x. Partial disorder of the crystal structure was found, i.e. the aluminium atoms partly exchange with the gadolinium and erbium atoms. The crystallographic ordering parameter y (defined as the number of aluminium atoms in the 8a sites) is equal to zero (“ideal ordering”) only for GdAl 2. It was observed that the parameter y increases with increasing x up to a content of about 30 mol.% ErAl 2. For this compound and for those with higher contents of ErA1 2 the exchange of the rare earth (gadolinium and erbium) and aluminium between the 8a and 16d sites is a maximum and equals about 1 atom per elementary cell.