Synthesis and structural properties of Nd3−xYxFe27.5Ti0.8Mo0.4(0 ⩽ x ⩽ 1.8) and Nd3−x′Yx′Fe27.8Mo1.2(0 < x′ ⩽ 2.8) intermetallic compounds

Alloys with compositions Nd3−xYxFe27.5Ti0.8Mo0.4 (0 ⩽ x ⩽ 1.8) and Nd3−x′Yx′Fe27.8Mo1.2 (0 < x′ ⩽ 2.8) have been synthesized and studied by means of X-ray powder diffraction and neutron powder diffraction. Rietveld analysis of XRD patterns reveals that the two series of compounds crystallize in monoclinic system with space group A2/m. It is found that higher starting yttrium content will make the synthesis of the Nd3−xYxFe27.5Ti0.8Mo0.4 and Nd3−x′Yx′Fe27.8Mo1.2more difficult. Substitution of Y for Nd leads to a contraction of the unit-cell volume and lattice parameters. The crystallographic structures and element site occupancies have been determined by neutron and X-ray powder diffraction and the results show that Ti and Mo prefer to occupy a 4g site and two 4i sites while Y prefers to enter the 4i sites, which are dominated by the site sizes or thermodynamics effects.