Study of the structural insertion of Al3+ in the Al2O3–SiO2 and Nd2O3–Al2O3–SiO2 glass systems

Glasses in the Al2O3–SiO2 and Nd2O3–Al2O3–SiO2 systems were prepared by the sol–gel method. The gel–glass evolution was studied using near-infrared (NIR) and ultraviolet–visible (UV–VIS) spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). The results obtained indicate a relationship between the sample compositions, the treatment temperature and the Al coordination. In the samples of the Nd2O3–Al2O3–SiO2 system the densification of the structure, when the treatment temperature increases, leads to the segregation of neodymium oxide particles.