In this study, the structure and substructure of SiO 2–Mg phosphate tungsten bronzes, MgPTB, (MgHPW 12O 40 · 29H 2O) obtained by ultrasonic spray pyrolysis method from a silica sol, and a MgPTB solution, obtained by the ion exchange method, as precursors were investigated. The mechanism of the formation of aerosol droplets is discussed. Phase composition, structure and substructure of SiO 2–MgPTB particles were investigated by X-ray powder diffraction (XRPD) analysis, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Good agreement between the theoretically predicted values for the mean diameters of particles and subparticles (1.27 μm and 75.4 nm, respectively) and the experimentally obtained ones (1.17 μm and 65–90 nm) was found. This agreement confirms the applicability of the model to get a satisfactory prediction of the most important data related to the nano-structural design of SiO 2–MgPTB powders.