Novel aspects in the chemistry of the non-aqueous fluorolytic sol–gel synthesis of nanoscaled homodisperse MgF2 sols for antireflective coatings

Abstract

Water-clear transparent sols of nano-MgF₂ and nano-MgF₂–CaF₂ composites in ethanol were synthesized through the fluorolytic sol–gel synthesis by the reaction of the insoluble precursor magnesium ethoxide with anhydrous hydrogen fluoride. CO₂, MgCl₂ or CaCl₂ are used as auxiliary reagents. The sols contain monodisperse nanoparticles with a size between 5 and 10 nm, depending on the particular synthesis method used. In contrast to all previous synthesis methods, the sols possess a low viscosity and offer a remarkably high long-time stability for more than one year. It has been demonstrated that they are very suitable for manufacturing antireflective porous coatings on glass substrates with remaining reflectivity below 1%, and high mechanical stability.