Structural changes in borosilicate glasses as a function of Fe2O3 content: A multi-technique approach
James D. Eales, A.M.T. Bell, Derek Cutforth, Albert A. Kruger, Paul A. Bingham
Abstract
Three series of borosilicate glasses were prepared, ranging from simple ternary sodium borosilicate glasses (SCFe series), to complex borosilicate glasses (CCFe Series), to high-level radioactive waste analogue glasses (HAFe series). 57Fe Mössbauer and Fe K-edge XANES spectroscopies showed that the iron exists exclusively as Fe3+ in predominantly distorted tetrahedral structures ([4]Fe3+), with evidence for lower abundances of higher-coordinated [5 or 6]Fe3+. Raman, B K-edge XANES, and XPS spectroscopies qualitatively demonstrated that Fe3+ preferentially integrates into the borosilicate network through the silicate sub-network in the simple glasses, whereas in the complex glasses it preferentially integrates through the borate sub-network. The [4]B3+ fraction for the SCFe and CCFe glasses showed minimal changes as a function of Fe content, indicating that Fe concentration has no effect on boron coordination and is- therefore unlikely to be competing with [4]B3+ groups for charge compensation, qualitatively supporting the presence of competing tetrahedral avoidance hierarchies.