Raman Spectra of Glasses of CaO-Ga2O3-GeO2 System

Raman spectra of undoped glasses of CaO-Ga2O3-GeO2 system with the garnet (Ca3Ga2Ge3O12) and Ca-gallogermanate (Ca3Ga2Ge4O14) structures are measured and analyzed. The spectra are interpreted on the basis of comparison to the well known Raman spectra of the garnet crystals with Ca3Ga2Ge3O12 and Ca3Sc2Ge3O12 structures. It is shown that the spectra observed for the glasses of CaO-Ga2O3-GeO2 system are almost independent of the basic glass composition. They consist of two broad bands centred near 535 and 825 cm-1, which belong to totally symmetric vibrational modes A1g of the mixed tetrahedral groups (structural units) (Ge/Ga)O4 available in the glass network. The interpretation of our results shows good correlation with the structural data obtained with EXAFS spectroscopy