Previously the non-cubic β-pyrochlore polycrystalline compounds Rb 0.95 Nb x Mo 2-x O 6.475-0.5x (x = 1.31-1.663) have been obtained in the ternary system Rb 2 O-Nb 2 O 5 -2MoO 3 . However, using special synthesis condition leads to the formation of cubic Fd-3m β-pyrochlore Rb 0.9 Nb 1.625 Mo 0.375 O 5.62 with small size particles and surface area of 15 m 2 /g. The Rb 0.9 Nb 1.625 Mo 0.375 O 5.62 powder has been investigated by X-ray powder diffraction analysis and scanning electron microscopy with X-ray microanalysis. The crystal structure refinement has been performed using the Rietveld method. The electronic structure and optical band gap of Rb 0.9 Nb 1.625 Mo 0.375 O 5.62 have been studied in comparison to similar non-cubic composition Rb 0.95 Nb 1.625 Mo 0.375 O 5.66 . The photocatalytic properties of Rb 0.9 Nb 1.625 Mo 0.375 O 5.62 have been investigated on the example for dyes solution oxidation under UV irradiation. The dependence on the photocatalytic properties of dye type and catalyst mass has been studied. It has been observed that the main oxidative species for dye oxidation is hydroxyl radicals. The phase and composition stability of catalyst powder have been confirmed.

Single crystals of CsNbMoO 6 were grown from solution in melt, and their crystal structure was solved by X-ray diffraction (R[I > 2σ(I)] 1 = 0.0386). Crystals were cubic, а = 10.41039(8) Å, Z = 8, space group F43m. The synthesized crystals were shown to exhibit the second harmonic generation effect, which confirmed the absence of an inversion center in the structure. The structure was built of MO 6 (M = Nb, Mo) octahedra, which share all vertices to form a three-dimensional framework where niobium and molybdenum atoms are randomly distributed. Framework interstices accommodate cesium ions. Crystals of CsNbMoO 6 can be considered as pseudo-symmetric with respect to space group Fd3m due to a small shift of some oxygen atoms relative to the regular system of points in this group.

No abstract

No abstract