Rb2Co1.85Ge1.15O6: The First Quaternary, Noncentrosymmetric Rubidium Cobalt Germanate

Abstract

Deep blue, prism-shaped, X-ray diffraction quality single crystals of a new quaternary rubidium cobalt germanate, exact composition Rb2Co1.85Ge1.15O6, were grown by soaking a pre-reacted polycrystalline powder in a molten RbCl/RbF eutectic flux (melting point = 546 °C) at 700 °C in a silver reaction vessel. The complex was characterized by single crystal X-ray diffraction and its elemental composition was semi-quantitatively confirmed by energy dispersive spectroscopy (EDS). Rb2Co1.85Ge1.15O6 crystallizes in the noncentrosymmetric orthorhombic space group C2221 with lattice parameters a = 6.5971(2) A, b = 9.8791(3) A and c = 10.8819(3) A in the K2ZnSi2O6 structure type. The crystal structure consists of a three-dimensional network, composed of Co and mixed Co/Ge tetrahedra, and features cavities occupied by Rb cations. X-ray diffraction quality single crystals of a novel rubidium cobalt germanate, Rb2Co1.85Ge1.15O6, were grown by soaking a pre-reacted powder, targeted for preparing Rb4.51Co2.35Ge5.10O15F1.96, in a RbCl-RbF eutectic melt at 700 °C. The complex was characterized by single crystal X-ray diffraction and found to crystallize in the orthorhombic space group C2221 in the K2ZnSi2O6 structure type.