SYNTHESIS AND LUMINESCENCE PROPERTIES OF K0,5xBi1-0,5x(MoxV1-x)O4 SOLID SOLUTIONS

Abstract

The conditions of heterovalent substitution in cationic and anionic positions of хK0,5Bi0,5MoO4 – (1-х)BiVO4 system within range of х = 0.1-0.9 with forming of К0,5xBi1-0,5x(MoxV1-x)O4 solid solutions, those possess scheelite-like type structure have been studied. All the samples of series were obtained by solid state technique. It was shown by IR spectroscopy and X-ray diffraction studies that molybdenum and vanadium occupying one crystallographic position with statistical distribution in х = 0.1–0.9 range of substitution. As result a lowering of lattice symmetry from tetragonal to monoclinic take place with increasing of molybdenum content. Charge compensation in system is realized through proportional substitution of bismuth by potassium in (К/Bi)O8 polyhedra. The data on diffuse reflectance indicate that increasing of substitution degree, x, lead to proportional increasing of band gap values from 2.33 to 2.72 eV for the semiconductors obtained. Intrinsic photoluminescence of the samples has been observed at low temperatures but is absent at room temperature. Total intensity of visible luminescence increases with increasing of molybdenum content in К0.5xBi1-0.5x(MoxV1-x)O4 solid solutions. Spectra of photoluminescence consist of wide two-component band with maxima at 620 and 705 nm, respectively. Simultaneous analysis of literature data and dependences of luminescence intensity on molybdenum content allow assumption that short-wavelength component related with centers, those formed on molybdate groups. Long-wavelength component related with vanadate groups. The wide bands at 375 and 410 nm in the photoluminescence excitation spectra were ascribed to absorption transitions in molybdate and vanadate oxyanions, respectively. The solid solutions studied can be used as hosts for luminescent ions or in elaboration of photocatalysts.