Phase relations and crystal structures in the system Ce–Ni–Zn at 800 °C

Abstract Phase relations have been established for the system Ce–Ni–Zn in the isothermal section at 800 °C using electron microprobe analysis and X-ray powder diffraction. Phase equilibria at 800 °C are characterized by a large region for the liquid phase covering most of the Ce-rich part of the diagram, whereas a Zn-rich liquid is confined to a small region near the Zn-corner of the Gibbs triangle. Whereas solubility of Ce in the binary Ni-Zn phases is negligible, mutual solubilities of Ni and Zn at a constant Ce content are large at 800 °C for most Ce–Zn and Ce–Ni compounds. The solid solution Ce(Ni 1− x Zn x ) 5 with the CaCu 5 -type is continuous throughout the entire section and for the full temperature region from 400 to 800 °C. Substitution of Zn by Ni is found to stabilize the structure of CeZn 11 to higher temperatures. At 800 °C Ce(Ni x Zn 1− x ) 11 (0.03≤ x ≤0.22) appears as a ternary solution phase. Similarly, a rather extended solution forms for Ce 2 (Ni x Zn 1− x ) 17 (0≤ x ≤0.53). Detailed data on atom site occupation and atom parameters were derived from X-ray structure analyses for single crystals of Ce 2+ y (Ni x Zn 1− x ) 17 , y =0.02, x =0.49 ( a =0.87541(3), c =1.25410(4) nm; Th 2 Zn 17 type with space group R 3 ¯ m , R F 2 = 0.018 ) and Ce(Ni 0.18 Zn 0.82 ) 11 ( a =1.04302(2), c =0.67624(3)nm, BaCd 11 type with space group I 4 1 / amd , R F 2 = 0.049 ).