Hydrothermal synthesis of hydrous vanadium oxide bronzes MxV3Oδ(VO)y · nH2O (M = K, Rb, Ba)

Hydrous vanadium (IV, V) oxides containing K or Rb were synthesized by the hydrothermal method from VOSO{sub 4}-M{sub 2}SO{sub 4} (M = K, Rb) solutions. they were found to be isomorphous with previously reported Ba{sub 0.4}V{sub 3}O{sub 8}(VO){sub 0.4}{center_dot}nH{sub 2}O, whose structure consists of V{sub 3}O{sub 8} layers which are bridged by V-O units (denoted by (VO){sub 0.4} in the formula) forming a tunnel-like opening to accommodate hydrous Ba ions. The isomorphous compounds can be formulated by J{sub x}V{sub 3}O{sub 8}(VO){sub y}{center_dot}nH{sub 2}O (M = K, Rb, Ba; n = 0.6--0.7) where x and y show similar values of less than 0.5 as is accounted for by the crystal structure. The formation of this phase seems to be governed by the size of M cation whose ionic radius should lie in a limited range of 1.35 to 1.52 {angstrom}. The V{sub 3}O{sub 8}(VO){sub y} framework structure of a bronze-like type is compared with the V{sub 2}O{sub 5} framework of {beta}-M{sub x}V{sub 2}O{sub 5} ({beta} bronze) and the V{sub 3}O{sub 8} framework of H{sub 2}V{sub 3}O{sub 8}.