Structural investigation and sonophotocatalytic properties of the solid solutions Sr(Mo1−xWx)O4 crystals synthesized by the sonochemical method

Abstract

In this paper, the solid solutions 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 properties were performed in function of the replacement of Mo6+ by W6+ cations into the lattice. Their structure and elemental composition were characterized using X-ray diffraction, Rietveld refinement, micro-Raman, energy-dispersive X-ray, and Fourier-transform infrared spectroscopies proving that all samples are monophasic, crystalline, and exhibit 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 is noted to pass through spindle-like morphology for the microcrystals containing both Mo6+ and W6+ cations (x = 0.25, 0.50, and 0.75). 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 bands with the increase in the concentration of W6+ cations in the lattice. Finally, we have obtained good sonophotocatalytic performances for SrMoO4 crystals (90%), and mainly to Sr(Mo0.25W0.75)O4 crystals (98%) in the degradation of Rhodamine B dye until 240 min under UV-C light.