THE STRUCTURE OF AL, FE, K SILICA-GERMANATE GLASSES INVESTIGATED BY RAMAN AND INFRARED-SPECTROSCOPY

Polarised Raman and Fourier transform infrared (FTIR) absorption spectra have been obtained for a series of glasses in the system SiO2(GeO2)Al2O3Fe2O3K2O in order to investigate changes in the glass structure with SiO2/GeO2 ratio. The results indicate that Ge4+ substitutes structurally for Si4+ in the tetrahedral network, and vibrational modes responsible for bands in the Al, Fe, K silicate or Al, Fe, K germanate glass spectra produce corresponding bands in the Al, Fe, K silica-germanate glass spectra. Systematic changes are observed in the polarisation characteristics, frequencies and intensities of spectral bands with variations of the SiO2/GeO2 ratio of these glasses. The changes observed in the Raman spectra with variation of SiO2/GeO2 ratio are analogous to those observed in the FTIR spectra of analysed glasses. Vibrational spectra of Al, Fe, K silica-germanate glasses have been compared to crystalline materials of the same composition in order to study the influence of the crystallization process on the structure of these glasses. The phase composition of samples undergoing crystallization was confirmed with X-ray diffraction (XRD). Raman and FTIR spectroscopic data of Al, Fe, K silica-germanate glasses demonstrated that the network of these glasses has corner-shared SiO4, GeO4 tetrahedra connected in a random structure. © 1990.