Synthesis, Crystal Structures, and properties of Edge-Sharing Tetrahedra Centered with Silicon and Cobalt: Cs_2CoSiO_4 and Cs_5CoSiO_6

摘要

Cs_2CoSiO_4 and Cs_5CoSiO_6 were obtained form reaction of Cs_2O, CdO and SiO_4 with cobalt plates in Ag containers which were encapsulated in glass ampoules under an Ar atmosphere. Cs_5CoSiO_6 is formed at 350 deg C (40 d) and Cs_2CoSiO_4 at 450 deg C (30 d) in an oxidation process under reduction of Cd~(2+) to the metal.Cs_2CoSiO_4 crystallizes in the space group CmC2_1 (A=582.1(1)pm, b=1243.3(3)pm,c=815.7(1)pm,R_(all)=0.006) and Cs_5CoSiO_6 in P2_1=(a=670.57(7)pm,b=1080.8(2)pm, c=1646.1(2)pm.#beta#=94.89(1),R_(all)=0.052).Both compounds have the characteristic feature of edge-sharing tetrahedra centered with cobalt and silicon, forming dimers in common. Magnetic and luminescence measurements were carried out for Cs_2CoSiO_4,and UV-VIS-NIR-MIR-FIR spectra were recorded for both compounds .The electronic structures are described in terms of the angular overlap model.