SYNTHESIS AND STRUCTURE OF NEW DOUBLE OXIDES OF MERCURY AND RARE-EARTH ELEMENTS - R2HGO4 (R = LA, ND, SM, EU, AND GD)

New double oxides with mercury and five rare earth elements, R2HgO4 (R =La, Nd, Sm, Eu, and Gd), were synthesized and characterized by X-ray powder diffraction, EDS analysis, electron microscopy, and thermal analysis. They all have the structure which was determined for one of the compounds, Nd2HgO4, from powder diffractometer data. Nd2HgO4 has a monoclinic unit cell, space group C2/m, Z = 4, and the cell parameters a = 13.8737(8)Å, b = 3.7936(4)Å, c = 10.240(2)Å, and β = 121.200(9)°. The mercury atoms are linearly coordinated to two oxygen atoms, and the two independent neodymium atoms coordinate seven oxygen atoms, which form polyhedra of slightly different shapes and sizes. © 1991 Academic Press, Inc.