Structural characterisation of tin fluorophosphate glasses doped with Er2O3

TL;DR

This study uses EXAFS and Raman microscopy to analyze the structural changes in tin fluorophosphate glasses doped with Er2O3, revealing bonding preferences, phase changes, and improved thermal stability with doping.

Contribution

It provides detailed structural insights into Er-doped tin fluorophosphate glasses, highlighting Er's bonding environment and effects on glass properties, which were previously uncharacterized.

Findings

Er prefers to bond with F atoms in the glass.

Addition of Er2O3 induces orthophosphate Q0 units.

Doping increases glass transition temperature and thermal stability.

Abstract

EXAFS and confocal Raman microscopy have been used to study 50SnF2.(20-x)SnO.30P2O5.xEr2O3 (x=0, 0.1, 0.25) glasses. EXAFS data reveal an average coordination of Sn to O of 1.5 in both undoped glass and Er-doped glass samples. The first coordination sphere of Er in glasses doped with Er2O3 was found to have 9 F atom neighbours at an average bond length of 2.292+/-0.005 {\AA}, indicating that Er preferentially bonds with F. Raman spectra clearly show the emergence of orthophosphate Q0 units on addition of Er2O3. The saturation of Er solubility is found to be between 0.25 and 0.5 mol$\%$ Er2O3. An increase of the glass transition temperature from $\sim$80{\deg}C in undoped glass to $\sim$87{\deg}C in samples doped with 0.25 mol$\%$ Er2O3 was also observed. This process is accompanied by an increase in the difference between the crystallisation and glass transition temperatures, which is usually associated with improved thermal stability of the glass.