R 5T 3 compounds (R ≡ rare earth; T ≡ Rh, Ir) with an Mn 5Si 3-type structure

Abstract

X-ray diffraction on a single crystal was used to establish the crystal structure of Ho 5Rh 3. A hexagonal structure of the Mn 5Si 3 type with space group P6 3/ mcm and lattice constants a = 8.100 A ̊ and c = 6.337 A ̊ was determined. Gd 5Rh 3, Tb 5Rh 3, Dy 5Rh 3, Er 5Rh 3, Tm 5Rh 3 and Lu 5Rh 3 are isostructural with Ho 5Rh 3. X-ray powder diagrams taken with a Guinier camera on the high temperature phase of R 5Ir 3 compounds (R ≡ Tb, Dy, Ho, Er, Tm, Lu) were indexed using Mn 5Si 3 structure parameters. A single-crystal study of Lu 5Ir 3 and Er 5Ir 3 showed weak superstructure reflections.