Structural study of spray dried silica–germanate nanoparticles

Noncrystalline materials belonging to 0.005Gd2O3·0.995[(1 − x)SiO2·xGeO2] system, with Si/Ge ratio ranging from 1:1 to 1:4 (x = 0.5; 0.667; 0.75; 0.8) were prepared by sol–gel and spray drying method. The samples were characterized by X-ray diffraction, scanning electron microscopy, electron paramagnetic resonance and nuclear magnetic resonance. The XRD patterns indicate that all prepared samples have an amorphous structure. The SEM imagines show that the samples are quite spherical conglomerates of amorphous nanoparticles. Gd3+ EPR spectra recorded from the gadolinium doped silica–germanate samples are specific for noncrystalline systems and show that gadolinium ions are mainly clustered on the nanoparticles surface. Solid-state 29Si MAS-NMR results indicate the Si/Ge ratio depending presence of Q2, Q3 and Q4 units in the silica–germanate samples, and a less polymerized silica network with increasing of germanium content.