Crystal structures, site occupations and phase equilibria in the system V-Zr-Ge

摘要

The V-Zr-Ge system was studied for two isothermal sections at 900 and 1200 deg C. Three ternary compounds VZrGe (tI12, I4/mmm, CeScSi-type), V_xZr_(5-x)Ge_4 (oP36, Pnma, Sm_5Ge_4-type) and V_(4+x)Zr_(2-x)Ge_5 (oI44, Ibam, Si_5V_6-type) were structurally characterized. Optical microscopy and powder X-ray diffraction (XRD) were used for initial sample characterization and electron probe microanalysis (EPMA) of the annealed samples was used to determine the exact phase compositions. The variation of the cell parameters of the various ternary solid solutions with the composition was determined. The three ternary phases were structurally characterized by means of single crystal and powder XRD. While VZrGe is almost a line compound, V_xZr_(5-x)Ge_4 (0.2 < = x < = 3.0) and V_(4+x)Zr_(2-x)Ge_5 (0.06 < = x < = 1.2) are forming extended solid solution ranges stabilized by differential fractional site occupancy of V and Zr on the metal sites.