Application of chromium-containing silica for synthesising functional glasslike materials by the sol-gel method

A new variant of the sol-gel method for synthesising silica glasses and optical composites containing nanoparticles of chromium oxide has been designed. Monolithic gels are produced by mixing preformed silica modified with chromium oxide (Cr2O3/SiO2), With a sol-gel solution containing Si(OC2H5)(4), and gelation catalyst ((CH2)(6)N-4 or NH3). Highly dispersed Cr2O3/SiO2 samples were synthesised through a step-by-step controlled adsorption of vapours of CrO2Cl2 and C6H14 on the surface of fumed silica (A-300) and a subsequent thermal decomposition. With increasing chromium concentration in samples from 0.9 to 5.1 wt.%, the size of chromium oxide nanoparticles increases from 10 to 46 nm. XRD, DTA, TG, IR-spectroscopy and measurements of specific surface area have been used to investigate structural and physico-chemical properties of Cr2O3/SiO2 and xerogels during the course of their thermal transformations up to formation of glasses. A study has also been carried out of optical properties of transparent samples (distribution of refractive index values through cross section of a preform). The glasses synthesised with the aid of Cr2O3/SiO2 have a more uniform distribution of doping constituents and exhibit a larger refractive index in comparison to glasses synthesised through impregnation of silica matrices with a solution of (NH4)(2)Cr2O7.