Roles of iron and lithium in silicate glasses by Raman spectroscopy

Raman spectroscopy has been used in a qualitative analysis of iron containing lithium silicate glasses. The iron was kept fixed at 8 mol% for all the iron containing samples with varying concentrations of Li2O and SiO2, as this resulted in samples that were fully vitreous in nature. The method of deconvolution of peaks in these data has been employed to understand the relative numbers of Q(0), Q(1), Q(2), Q(3), and Q(4) silicate structural units. Even though the iron concentration is constant, the linkages of silicate structural units show variation with increasing alkali content. The roles of lithium and iron have been found to be opposed to each other in that the presence of lithium discourages formation of tetrahedral linkages in the structure, whereas iron promotes corner connected tetrahedra or the presence of bridging oxygens.