Structural characterisation of Er-Si-Al-O-N glasses by Raman spectroscopy

Er-Si-Al-O-N glasses have been prepared with cation ratio Er:Si:Al = 3.45:3:2 containing various amounts of nitrogen (N = 0, 5, 8, 15 and 22 equiv.%). Glass properties such as microhardness, glass transition temperature and dilatometric softening temperature were measured and it was found that these properties increased linearly with increasing nitrogen content. Glasses were then characterised using Raman spectroscopy in order to obtain information about the structure of these glasses. Deconvolution of peaks in the Raman spectra of Er-Si-Al-O-N glasses revealed that, as nitrogen content increases then the proportion of Q³ species decreases and there is a corresponding increase in the proportion of Q⁴ species (Qⁿ: n = no. of bridging anions joining SiO₄ tetrahedra), confirming that nitrogen increases the crosslinking between individual tetrahedra via the transformation of Q³ oxide species into Q⁴ oxynitride species.