Phase relationships and crystallography of annealed alloys in the Ce 5Si 4–Ce 5Ge 4 pseudobinary system

Abstract

The phase relationships of annealed alloys in the Ce 5Si 4− x Ge x system were determined by X-ray powder diffraction (XRD). Two structurally distinct terminal phase regions were observed in this system: the Ce 5Si 4-based solid solution (0 ≤ x < 2.85) crystallizing in the Zr 5Si 4-type tetragonal structure with space group P4 12 12, and the Ce 5Ge 4-based solid solution (3.35 < x ≤ 4) crystallizing in the Sm 5Ge 4-type orthorhombic structure with space group Pnma. An intermediate phase, which has a narrow composition range with the monoclinic Gd 5Si 2Ge 2-type structure, space group P112 1/ a, was found to exist at x = 2.95 ± 0.05. The Rietveld powder diffraction profile fitting technique was used to refine the crystal structures, lattice parameters, and the atomic positions. The phase relationships of the Ce 5Si 4− x Ge x pseudobinary system after heat treatment were established from these data.