Effect of fluoride ions on the preparation of transparent glass ceramics based on crystallization of barium borates

Formation of transparent glass-ceramics based on crystallization of barium borate (BBO) crystals from BaO·B2O3 glass-systems, with and without addition of BaF2 has been investigated. Crystallization of glass-samples was done by controlled thermal heat-treatment, at nucleation and crystallization temperatures, for different times and rates. When the glasses were heat-treated at the nucleation temperature, transparent glass-ceramics containing 0.1–0.3 μm BBO crystals were prepared. It is obvious that fluorine influences the transparency of glass-ceramics.