Synthesis and characterization of solid solution of Sr(Mo1-xWx)O4 crystals obtained by the sonochemical method and their sonophotocatalytic properties

Abstract In this paper, the solid solution of strontium molybdate-tungstate [Sr(Mo1-xWx)O4] crystals with (x = 0; 0.25; 0.50; 0.75; and 1) were synthesized by the sonochemical method. Their structure, morphology, optical, and sonophotocatalytic (SPC) properties were evaluated as a function of the replacement of Mo6+ by W6+ cations into the lattice. Structural characterizations performed by X-ray diffraction, Rietveld refinement, micro-Raman, and Fourier transform infrared spectroscopies proved that all samples are monophasic and crystalline, with a scheelite-type tetragonal structure. Field-emission scanning electron microscopy images revealed the octahedral and dumbbell-like morphologies for SrMoO4 and SrWO4 crystals. Moreover, it was noted to pass through spindle-like morphology for the microcrystals containing both Mo6+ and W6+ cations (x = 0.25; 0.50; and 0.75). The absorption spectra obtained through ultraviolet-visible diffuse reflectance spectroscopy showed a directly proportional increase in the optical band gap (Egap) values from 4.27 to 5.01 eV. These data indicate an increase in the intermediary electronic levels between valance and conduction band with the raise of the concentration of W6+ cations in the lattice. Finally, we have found that the Sr(Mo0.25W0.75)O4 crystals displayed the best SPC activity, around 98% of the Rhodamine B dye was degraded in 240 min.