Isothermal section of the Dy‒Ge‒Si system at 600 C

Abstract

The interaction of the components in the ternary Dy–Ge–Si system was investigated by means of X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The isothermal section of the Dy–Ge–Si phase diagram was constructed at 600 °C for the first time. The alloys for the investigation were synthesized by arc melting the metals (purity of the elements higher than 99.9 wt.%) in an arc furnace under argon atmosphere. The alloys were annealed at 600 °C in evacuated quartz tubes for 720 h, and subsequently quenched in ice water, and examined by X-ray powder diffraction (DRON-4.07 diffractometer, Fe K α-radiation). The crystal structures of the phases were refined using the program DBWS-9807. The chemical and phase compositions of the samples were examined by Scanning Electron Microscopy (SEM) (REMMA-102-02 electron microscope). The existence of continuous solid solutions between the isostructural binary germanides and silicides delimiting the Dy 5 Si 3-x Ge x (Mn 5 Si 3 -type structure), Dy 5 Ge 4-x Si x (Sm 5 Ge 4 -type structure), DyGe 1-x Si x (CrB-type structure), and DyGe 1.5-x Si x (AlB 2 -type structure) ranges was established. Limited solid solutions were observed based on the binary germanides DySi 1.67 (α-GdSi 2 -type structure) and Dy 11 Ge 10 (Ho 11 Ge 10 -type structure). The solubility of Ge in the compound DySi 1.67 is 0.20 at. part, the solubility of Si in the compound Dy 11 Ge 10 is ~0.07 аt. part. The ternary compound DyGeSi 0.75 was found: α-ThSi 2 -type structure, Pearson symbol tI 12, space group I 4 1 / amd , a = 4.052(3), c = 13.6207(10) Å, V = 221.78(3) Å 3 , R B = 0.1011, R p = 0.0318, R wp = 0.0437. Keywords : rare-earth metal, germanide, silicide, phase diagram, solid solution, crystal structure.