A Raman spectral study has been carried out on the structure of the glassy and molten states of the binary silicates, Li2O-SiO2, Na2O-SiO2, K2O-SiO2, CaO-SiO2, SrO-SiO2 and BaO-SiO2.
An argon-ion laser beam of 4 880 A has been used as an exciting light for the glassy state and 4 579 Å for the molten state. New discrete Raman lines have been observed clearly in the quenched glassy samples. These spectra are compared with those measured in the crystallized stoichiometric silicates. The silicate formation by mixing basic oxides with vitreous silica induces a shift of the line at 485 cm-1 toward higher wave number. This shift does not depend on the species of alkali or alkaline earth elements but on the composition of a basic oxide. The spectra of the glassy state exhibit four different peaks in the Raman shifts between 850 and 1 100 cm-1 corresponding to the number of non-bridging oxygens for each silica tetrahedron unit.
Raman spectra of the alkali silicate systems have been measured below and above their melting points. There is little difference in the spectra between the quenched glassy state and the molten state. The silica tetrahedron complex structure, therefore, is relatively stable in these systems and the Si-O bond stretching and Si-O-Si bending vibrations are not affected by thermal energy up to 1 353 K.
