New layered compounds with honeycomb ordering: Li _3Ni _2BiO _6, Li _3NiM′BiO _6 (M′ = Mg, Cu, Zn), and the delafossite Ag _3Ni _2BiO _6

摘要

The new layered compound Li _3Ni _2BiO _6 has been prepared by a solid-state reaction. It crystallizes in the monoclinic C2/m space group; its lamellar structure is characterized by a honeycomb ordering between Ni ~(2+) and Bi ~(5+) within the slabs, while Li ~+ ions occupy octahedral sites in the interslab space. Stacking defects weakly alter the XRD pattern. By substitution of half of the nickel ions, the new phases Li _3NiM′BiO _6 (M′ = Mg, Cu, Zn) isostructural with Li _3Ni _2BiO _6 have been synthesized under similar conditions. All these compounds demonstrate paramagnetic behavior at high temperature, and Li _3Ni _2BiO _6 exhibits an antiferromagnetic ordering at 5.5 K. By topotactic molten salt ionic exchange, the new delafossite compound Ag _3Ni _2BiO _6 has been also obtained and characterized.