Reinvestigation of the isothermal section of the Ce–Co–Ge ternary system, at 700 °C

The solid state phase equilibria in the Ce–Co–Ge ternary system at 700 °C were investigated by means of X-ray diffraction and scanning electron microscope–energy dispersive X-ray spectroscopy. A total number of nine intermediate phases were characterized and the homogeneity ranges of the various ternary solid solutions of the binary boundary systems (Ce–Co, Ce–Ge and Co–Ge) were studied. The new ternary phase, CeCo13−xGex (4 ≤ x ≤ 4.5) has been discovered. It crystallizes in the tetragonal space group I4/mcm (no. 140), with the cell parameters a = 7.974(5) Å and c = 11.856(5) Å for x = 4. CeCo9Ge4 derives from the CeNi8.5Si4.5-type, but, with a perfect ordering of the atoms on the crystallographic sites. The phase diagram comprises seven extensions of binaries into the ternary system, eight stoichiometric ternary phases, CeCoGe, CeCo2Ge2, CeCoGe3, Ce2Co3Ge5, Ce2CoGe3, Ce3CoGe2, Ce5CoGe2 and Ce5Co4Ge13 and two intermediate solid solutions, CeCo1−xGe2 (0 ≤ x ≤ 0.24) and CeCo13−xGex (4 ≤ x ≤ 4.5).