Interfacial reactions and silicate formation in high surface SiO 2 impregnated with La nitrate

Abstract

Solid state interface reactions in high surface SiO 2 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 La O Si layer covering SiO 2 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. La 6[Si 4O 13][SiO 4] 2 silicate forms at temperatures from 950 °C as the first, quasi two-dimensional phase, and then, at higher temperatures, A-La 2Si 2O 7 silicate occurs. Mechanism of formation of lanthanide silicates in high surface SiO 2 impregnated with Ln nitrates is proposed.