Phase relationships and crystallography of annealed alloys in the Ce5Si4–Ce5Ge4 pseudobinary system

The phase relationships of annealed alloys in the Ce5Si4−xGex system were determined by X-ray powder diffraction (XRD). Two structurally distinct terminal phase regions were observed in this system: the Ce5Si4-based solid solution (0 ≤ x < 2.85) crystallizing in the Zr5Si4-type tetragonal structure with space group P41212, and the Ce5Ge4-based solid solution (3.35 < x ≤ 4) crystallizing in the Sm5Ge4-type orthorhombic structure with space group Pnma. An intermediate phase, which has a narrow composition range with the monoclinic Gd5Si2Ge2-type structure, space group P1121/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 Ce5Si4−xGex pseudobinary system after heat treatment were established from these data.