A research team led by Prof. Dr. WANG Pengfei from Xi'an Institute of Optics and Precision Mechanics (XIOPM) of the Chinese Academy of Sciences (CAS) reveals the relationship between F/O ratio and the structure of fluorophosphate glass through conducting comprehensive research of Raman spectroscopy and nuclear magnetic resonance (NMR).
The result was published in Journal of Non-Crystalline Solids.
The performance of fluorophosphate glass is closely related to its structure. However, the conclusions drawn from all the studies on its structure so far cannot be universally applied to glasses with different compositions. Since F- and O- are the only two existing anions and play a dominant role in its structure, studying the common structural features of glasses by F/O ratio is an efficient approach.
In this work, researchers prepared series of glass samples based on the fluorophosphate system with a F/O ratio of 1-7. The content changes of different Qn groups under different F/O ratio were studied by Raman spectra and NMR.
Further, researchers concluded quantitative relationship between F/O ratio and Qn characteristics through comparative analysis of reported NMR spectra.
When the F/O ratio is below 0.3, Q2 content is highest, while the unit presence of Q0 is very small, and the percentage is less than 10%.
When the F/O ratio is in the range of 0.3 to 1, the Qn units with the highest content is composed of Q2 or Q1 units. With the increase of the F/O ratio, the content of Q1 increased significantly, while the content of Q0 remained relatively stable within this range.
When the F/O ratio is in the range of 1 to 4, the Qn units with the highest content include Q0 or Q1 units.
When the F/O ratio is more than 4, it is shown that the Qn units with the highest content is composed of Q0. With the increase of oxygen content ratio, the growth rate of Q0 slows down and approaches saturation.
This research reveals the general rule of the effect of F/O ratio on the structure of fluorophosphate glass, which provides an effective way to predict the structure and properties of glass by composition.
Structural schematic diagrams of QnmF units and the transition process. (Image by XIOPM)
Percentage of Qn units based on NMR results of different fluorophosphate glasses. (Image by XIOPM)
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