Transparent oxyfluoride glass-ceramics obtained by different sol-gel routes

Oxyfluoride glass-ceramics (OxGC) present attractive optical properties suitable for many applications. The incorporation of fluoride crystals into silicate matrices improves the luminescence properties, producing materials appropriate for photonic applications. Many papers focus on the preparation of oxyfluoride glass ceramics by melting quenching (MQ), the most widely utilized process. However, in the last decades, the sol-gel process has gained increasing interest as an alternative method for avoiding the MQ drawbacks. The first sol-gel route for producing glass-ceramics with rare earth (RE) doped fluoride nanocrystals were based on the preparation and further mixing of two separate sols. The crystallization of the fluoride nanoparticles occurs during the controlled thermal treatment. More recently, a new sol-gel strategy was proposed, based on the previous synthesis of aqueous fluoride nanoparticles suspensions that are subsequently dispersed in a silica sol-gel matrix. This paper summarizes the most relevant results as well as the advantages and disadvantages of each route and their limitations for future industrial scale up. The synthesis routes are compared considering the structural and morphological characterization, elucidating the crystallization mechanisms, and evaluating the optical properties of the resulting materials. Particular attention is paid to the possibility of producing transparent oxyfluoride glass ceramics films with improved luminescence and enhanced optical properties.

Automated summary

Oxyfluoride glass-ceramics exhibit attractive optical properties for photonics applications. Traditional preparation methods involve melting quenching, but in recent years, the sol-gel process has gained attention as an alternative. There are two sol-gel routes available for producing oxyfluoride glass-ceramics.