The crystal structure of stabilized by gallium Laves phase Zr1-xGaxRu2 (x = 0.18)

The new ternary phase Zr 1- x Ga x Ru 2 ( x = 0.18) was synthesized by arc melting the components followed by annealing at 870 K for 1400 h. Its crystal structure was studied by the X-ray diffraction (full-profile Rietveld mode) and energy-dispersive X-ray spectroscopy of the Zr 36 Ru 58 Ga 6 sample: structure type MgZn 2 , space group P 6 3 / mmc , a = 5.1399(1), c = 8.4888(2) Å. Gallium atoms replace larger zirconium atoms in the 4 f position, forming a statistical mixture of composition M = 0.82Zr + 0.18 Ga. Ruthenium atoms occupy positions 2 a and 6 h in the structure. Ru–Ru distances with the values from 2.533 to 2.605 Å are intermediate between the sum of covalent (2x1.25 = 2.50 Å) and metallic (2x1.325 = 2.65 Å) radii of ruthenium atoms. M –Ru distances in the structure are larger than the sum of the metallic radii of zirconium and ruthenium (1.60 + 1.325 = 2.925 Å). Probably, a slight gallium doping (6 at. %) of the HT binary compound ZrRu 2 with the MgZn 2 -type structure (existence temperature interval 2098–1558 K) leads to its stabilization at lower temperatures with the formation of the Zr 1- x Ga x Ru 2 ( x = 0.18) phase. The limits of the neighbor RuGa 1- x Zr x solid solution were refined: CsCl-type structure, space group Pm -3 m , 0 ≤ x ≤ 0.50; a = 3.0101(1) – 3.2264(2) Å. Keywords : intermetallic compounds, crystal structure, ternary system, phase equilibria.