The ternary system Eu–Cu–Ge at 400°C

Abstract

The isothermal section at 400°C of the phase diagram of the system Eu-Cu-Ge was built based on X-ray diffraction and microstructure analysis. The compound EuCu 2 Ge 2 (CeAl 2 Ga 2-type structure) was confirmed and its homogeneity region was determined: EuCu 2.5-1.65 Ge 1.5-2.35. In addition, three other ternary compounds were found: EuCuGe (HoNiGa-type structure), EuCu 0.8-0.5 Ge 1.2-1.5 (AlB 2-type structure), and ~Eu 2 Cu 2 Ge (unknown structure). The effective valence of Eu in EuCu 0.8 Ge 1.2 was found to be 2+. The existence of a binary homogeneity range Eu 1-x Cu 5+2x was confirmed by complete structure refinements.

Experimental Study of the Y-Cu-Ge System at 870 K

“…RCuGe germanides, where R are light rare earths, crystallize in the AlB 2 -type whereas for rare earths of Yttrium group equiatomic compounds belong to the CaIn 2 (or ordered LiGaGe) type structure and the ternary phases R(Сu,Ge) 2 with AlB 2 -type were realized at deviated composition along 33 at % of R. Contrary to the AlB 2 -type equiatomic compounds with Ce and Eu, the existence of the equiatomic CeCuGe and EuCuGe germanides with CaIn 2type was found at higher annealing temperature (1073 K) [23]. The EuCuGe compound with the orthorhombic HoNiGa-type was realized in the Eu-Cu-Ge system at 670 K [24]. As a conclusion, the formation of the R(Сu,Ge) 2 and RСuGe compounds depends on both the nature of the rare earths and the temperature of annealing.…”