Lanthanide ion (Ln³⁺)-doped oxyfluoride glass-ceramics have garnered considerable attention recently, owing to their wide and promising application in solid-state lasers, optical amplifiers and optical displays.

So far, most of the studies have been focusing on precipitation of different crystals and obtainment of fascinating optical properties. However, the glass structural dependence on compositions and the glass structural evolution during crystallization, which play critical roles in understanding the formation mechanism of these materials, have been rarely studied due to the complexity of glass structure.

Recently, researchers from Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences (SIOM, CAS) have reported a comprehensive structural study in atomic-level of the fluoro-phosphate glass ceramics containing Er³⁺-doped Na₅Y₉F₃₂ crystals. The results were published in Journal of Materials Chemistry C.

In their experiment, they used multiple advanced solid state nuclear magnetic resonance (SSNMR) techniques and luminescence spectra. Based on the SSNMR results and luminescent spectra, they found a novel structure evolution mechanism during the crystallization, where M represents the positive ions Na⁺, Ba²⁺, and Y³⁺.

The study proves that rare earth ions do not show any preference for selectively entering the fluoride crystals than for staying in the glass matrix during crystallization.

This novel structure evolution mechanism indicates that the distribution of rare earth ions during crystallization is not as simple as the past consensus that REI selectively aggregate into fluoride crystals after crystallization.

Furthermore, they have also found the prerequisites of crystal precipitation, which is significant for the design of glass compositions.

This work presents a profound insight of oxyfluoride glasses and glass ceramics with optical functions and a novel investigation strategy of oxyfluoride glass-ceramics.

This work was supported by the National nature science foundation of China.

Precipitation of Er³⁺-doped Na₅Y₉F₃₂ crystals from fluoro-phosphate glasses. (Image by SIOM)