Crystal structure of R₁₅Ni_96−xGa_x (R ≡ Sm, Y, Tb, Dy, Er, Tm, Yb, Lu)

The structure of the compound Sm15Ni52Ga44 was investigated by means of single-crystal methods (autodiffractometer "Syntex" P2(1), Mo K-alpha, graphite monochromator): space group P6m2BAR, a=8.771(1) angstrom; c=25.061(4) angstrom, Z=15, R(F)=0.079 for 391 reflections using the isotropic approximation for thermal parameters. The shortest interatomic distances are: Sm-Sm, 3.87; Sm-Ga, 2.76; Sm-Ni, 2.66; Ga-Ga, 2.20; Ni-Ni, 2.32; Ni-Ga, 2.30 angstrom. The coordination numbers for the atoms are: samarium, 18-20; nickel, 11, 12, 14; gallium, 11, 12, 14

CeNi₃-type ternary phases in the RNiGa systems (R ≡ Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)

Ternary gallides RNi(3-x)Ga(x) (R equivalent to Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) have been investigated by means of Xray phase and structure analyses. The new compounds were all found to be isotypic; in the case of YNi2.5Ga0.5 the structure type was refined from powder diffraction data (CeNi3 type of structure, space group P6(3)/mmc, Z=6, R(I)=0.124). At 600 degrees C all the RNi(3-x)Ga(x) compounds have homogeneity ranges between x=0.12 and 1.00. The electrical properties of the DyNi2.68Ga0.32, HoNi2.2Ga0.8, TmNi2.44Ga0.56 and LuNi2.44Ga0.56 compounds were investigated in the temperature range 77 K<T<363 K. All of them have metallic-type conductivity