Synthesis, Structural Characterization and Physical Properties of a New Member of Ternary Lithium Layered Compounds - Li2RhO3

Li2RhO3 was synthesized by solid state reaction and its crystal structure was refined from X-ray powder data by the Rietveld-method. The compound was obtained as a black powder and crystallizes in the monoclinic space group C2/m, with unit cell parameters a = 5.1198(1), b = 8.8497(1), c = 5.1030(1) angstrom, beta = 109.61(2)degrees, V = 217.80(1), and Z = 4. The structure determination shows that the oxygen atoms in Li2RhO3 form an approximate cubic close packing, where all octahedral voids are occupied by Rh4+ and Li+ cations. The structure is closely related to the alpha-NaFeO2 and Li2MnO3 layered structure types (layered variants of the NaCl-type), but in Li2RhO3 the lithium and rhodium atoms are partially disordered. Li2RhO3 behaves as a semiconductor with rather small activation energy of 7.68 kJ.mol(-1) and is thermally stable up to 1273 K in argon atmosphere. According to measurements of the magnetic susceptibility in the temperature range from 2 to 330 K, Li2RhO3 is paramagnetic, obeys the Curie-Weiss law at temperatures above 150 K, and has an effective magnetic moment of 1.97 mu(B) at 300 K.