Pressure-assisted sintering approaches for up-converting LiYF4:Er/Yb transparent oxyfluoride glass-ceramics

Glasses of compositions 40SiO2-25Al2O3-18Li2O-7LiF-(10-x-y)YF3-xErF3-yYbF3 (mol.%, x = 0.1, 0.5; y = 0, 0.4, 2, 4) were prepared by melt-quenching technique and milled into powders. Glass powder pellets were treated by hot pressing at defined temperatures to obtain the corresponding glass-ceramics (GCs). High-resolution TEM and XRD analysis revealed the crystallization of LiYF4 and LiAlSiO4 phases with nano-crystal size below 50 nm, resulting in translucent GCs. The density of GCs was 98-99.5 % compared to parent glasses. GCs exhibited intense up-conversion emission when excited by near-infrared light at 980 nm. As Er3+ concentration increased from 0.1 to 0.5 mol.% in the samples, notable enhancement in green and red emission intensities was indicated. Yb3+ ions significantly facilitated up-conversion emission through energy transfer to Er3+ ions, resulting in a higher luminescence yield compared to Er3+ single-doped GCs. The tuning of the red to green emission intensity ratio can be achieved by varying Er3+ and Yb3+ concentrations and Er3+/Yb3+ ratio.