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In this paper, the solid solutions of strontium molybdate-tungstate [Sr(Mo 1-x-W x )O 4 ] 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 Mo 6? by W 6? 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 SrMoO 4 and SrWO 4 crystals. Moreover, it is noted to pass through spindle-like morphology for the microcrystals containing both Mo 6? and W 6? cations (x = 0.25, 0.50, and 0.75). Ultraviolet-visible diffuse reflectance spectroscopy showed a directly proportional increase in the optical band gap (E gap ) 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 W 6? cations in the lattice. Finally, we have obtained good sonophotocatalytic performances for SrMoO 4 crystals (90%), and mainly to Sr(Mo 0.25 W 0.75 )O 4 crystals (98%) in the degradation of Rhodamine B dye until 240 min under UV-C light.