Syntheses and Crystal Structure Characterizations of New Rare Earth Nickel Bismuth Compounds RNixBi2 (R = Y, Gd Tb and Dy)

The title new compounds with chemical formula RNixBi2 were synthesized by are melting method followed by annealing. The crystal structures refined by using Rietveld method and X-ray powder diffraction data are isotypic to CaMnBi2 structure type, space group P4/nmm with a =0.448350(4), c = 0.930026(2) nm, V = 0.186952(7) nm^3 for YNi0.82Bi2, a = 0.448882(5), c =0.93658(2) nm, V = 0.188715(8) nm^3 for GdNi0.86Bi2, a = 0.448486(3), c = 0.93062(2) nm, V =0.187185(6) nm^3 for TbNi0.78Bi2 and a = 0.447493(4) nm, c = 0.925852(1) nm, V = 0.185402(6)nm^3 for DyNi0.77Bi2, showing lanthanide contraction. The structure is characterized by layers of edge-sharing NiBi4 tetrahedron and covalently bonded Bi square net separated by rare earth atoms.