The Transformation from Translucent into Transparent Rare Earth Ions Doped Oxyfluoride Glass-Ceramics with Enhanced Luminescence

It is known that the optical transparency of an oxide glass decreases with an increase in the size and fraction of crystals in the glass during heat-treatment. Here, the authors report an opposite scenario, where a translucent Er3+-Yb3+ doped oxyfluoride precursor glass-ceramic (P-GC) becomes transparent with increasing crystal size and crystallinity. Specifically, in the heat-treated P-GC samples, the authors observe that the growth of the existing Ba2LaF7 crystals and particularly the formation of small spherical Ba2LaF7 crystals greatly enhanced the light transmittance. To reveal the origin of this anomalous phenomenon, the authors perform detailed morphology and structure analyses on both P-GC and the heat-treated P-GC samples and molecular dynamics simulations of the precursor glass. The results show that the composition of the residual glass phase is altered (e.g., depletion of La3+) in the way that the differences in refractive index between the glass matrix and the crystals are greatly reduced. As a consequence, the light scattering of the heat-treated P-GC is suppressed, and hence, the derived P-GC becomes transparent. In addition, a proper heat-treatment can also enhance the luminescence of the studied P-GC system.

Automated summary

In the process of heat treatment, the authors discovered that the optical transparency of a specific oxyfluoride precursor glass-ceramic (P-GC) increases with an increase in crystal size and crystallinity. They also observed that the growth of existing crystals and the formation of small spherical crystals greatly enhanced light transmittance. Through detailed morphology and structure analysis and molecular dynamics simulations, the authors found that the composition of the residual glass phase changed, leading to a reduction in the differences in refractive index between the glass matrix and the crystals. Consequently, the light scattering of the heat-treated P-GC was suppressed, resulting in transparency. Furthermore, proper heat treatment also enhanced the luminescence of the studied P-GC system.