Transparent Sol-Gel Oxyfluoride Glass-Ceramics with High Crystalline Fraction and Study of RE Incorporation

Transparent oxyfluoride glass-ceramic films and self-supported layers with composition 80SiO(2)-20LaF(3) doped with Er(3+) have been successfully synthesized by sol-gel process for the first time. Crack-free films and self-supported layer with a maximum thickness up to 1.4 µm were obtained after heat treatment at the low temperature of 550 °C for 1 min, resulting in a LaF(3) crystal fraction of 18 wt%, as confirmed by quantitative Rietveld refinement. This is the highest value reported up to now for transparent oxyfluoride glass-ceramics prepared by sol-gel. This work provides a new synthesis strategy and opens the way to a wide range of potential applications of oxyfluoride glass-ceramics. The characterization by a wide range of techniques revealed the homogeneous precipitation of LaF(3) nanocrystals into the glass matrix. X-ray absorption spectroscopy and electron paramagnetic resonance confirmed that the Er(3+) ions are preferentially embedded in the low phonon-energy LaF(3) nanocrystals. Moreover, photoluminescence (PL) measurements confirmed the incorporation of dopants in the LaF(3) nanocrystals. The effective concentration of rare-earth ions in the LaF(3) nanocrystals is also estimated by X-ray absorption spectroscopy.