Influence of aluminium and neodymium additions on the structural relaxation of silica glasses - Raman investigations

Abstract

Raman spectra of silica glasses obtained from melted rock crystal without additions and of glasses doped with aluminium and neodymium were examined. The relative intensity of the 606 cm^-1 band in Raman spectra was evaluated. The occurrence of this band is due to the presence of defects in the glass structure. The time required by the 606 cm^-1 band to attain the equilibrium intensity at 1000 °C has been defined as the relaxation time of the silica glass structure under the given conditions of heat treatment. It has been found that additions in silica glass in the form of Al3+ and Nd3+ ions do not affect the value of the equilibrium intensity of the 606 cm^-1 band and thus, they do not affect the equilibrium concentration of the defects which give rise to this band. However, the additions have a distinct effect on the length of the relaxation time of the glass structure. Neodymium, when occurring as a single addition of silica glass, reduces the relaxation time, whereas aluminium clearly makes the structure relaxation difficult. Glass doped both with aluminium and neodymium (Al2O3/Nd2O3 = 4) behaves similarly as glass doped with aluminium only. The role of additions in the structure of silica glass was discussed on the basis of the investigation results.