Structure of borosilicate glassy materials with high concentrations of sodium, iron, and aluminum oxides

Alkali borosilicate glassy materials, which contain high iron and aluminum oxide concentrations and simulate vitrified high-level wastes of the Savannah River Site (United States), are investigated using X-ray powder diffraction, optical and electron microscopies, and infrared spectroscopy. The materials prepared by induction melting in cold crucibles operating in pilot and industrial facilities at the State Unitary Enterprise “Moscow Research and Production Association Radon” consist of a glass matrix with distributed individual or aggregated crystals of spinel similar in composition to trevorite. The maximum content of the crystalline phase in the glassy material from a “dead volume” of the cold crucible with an industrial size reaches ∼13 vol %. The texture of the glass phase is complex and determined by the direction of flows in cold crucibles under the action of eddy currents, the character of outflow of the glass melt stream during pouring into canisters, and the interaction of the stream with the glass solidified in the canister after preceding pourings. The structure of the anionic motif of the glass phase is predominantly built up of metasilicate chains and boron-oxygen fragments with threefold-coordinated boron.