X-ray investigation of alloys on the cross sections RGe2–LuGe2 (R – Pr, Nd) and SmGe2–R′Ge2 (R′ – Gd, Tb, Ho, Er, Tm)

Abstract

The experimental data on ternary R – R ′–Ge systems, where R and R ′ – rare earth metals of cerium or yttrium subgroups, are available in the literature. The investigations were mainly devoted to the sections between digermanides R Ge 2 – R ′Ge 2 . Alloys of the quasi-binary section R Ge 2 –LuGe 2 ( R – Pr, Nd) and SmGe 2 – R ′Ge 2 ( R′ – Gd, Tb, Ho, Er, Tm) annealed at 870 K were investigated by means of X -ray phase and structural analyses, and energy-dispersive X -ray spectroscopy. The alloys for the investigation were synthesized by arc melting of pure metals (purity of the elements higher than 99.9 wt. %) in an arc furnace under argon atmosphere. The alloys were annealed at 870 K in evacuated quartz tubes for 720 h, and subsequently quenched in ice water, and examined by powder X-ray diffraction (DRON-4.07 diffractometer, Fe K α-radiation). The crystal structure of the compounds was refined by the Rietveld method using the program FullProf. The alloys of cross sections R Ge 2 –LuGe 2 ( R – Pr, Nd) contains two phase wth α -ThSi 2 and ZrSi 2 structure types. The alloy Nd 0 . 16 Lu 0 . 18 Ge 0 . 66 contain one phase. The alloys of cross sections SmGe 2 – R ′Ge 2 ( R ′ – Gd, Tb) contain only one phase with α -ThSi 2 structure type. Isostructure ternary phases with the composition Sm 1- x R ′ x Ge 2 (structure type TbGe 2 ), R ′ – Ho, Er, Tm are formed. The polycrystalline samples Pr 0 . 22 Lu 0 . 12 Ge 0 . 66 , Nd 0 . 22 Lu 0 . 12 Ge 0 . 66 , Nd 0 . 19 Lu 0 . 15 Ge 0 . 66 and Sm 0 . 16 Ho 0 . 18 Ge 0 . 66 were investigated by X -ray energy spherical spectroscopy. Keywords : rare-earth metal, X -ray phase analysis, X -ray structure analysis, energy dispersive X -ray spectroscopy, phase equilibria, crystal structure, structure type.