Interfacial reactions and silicate formation in high surface SiO2 impregnated with La nitrate

Solid state interface reactions in high surface SiO2 impregnated with lanthanum nitrate were studied at temperature 600-1200 °C with X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier Transform Infrared spectroscopy (FTIR) and Raman spectroscopy. The results show that at 600-900 °C an amorphous, nanometer thick LaOSi layer covering SiO2 particles exists in the system. At higher temperatures the breakage of the layer into amorphous islands occurs and crystalline silicates with various structures are formed. La6[Si4O13][SiO4]2 silicate forms at temperatures from 950 °C as the first, quasi two-dimensional phase, and then, at higher temperatures, A-La2Si2O7 silicate occurs. Mechanism of formation of lanthanide silicates in high surface SiO2 impregnated with Ln nitrates is proposed.