PHYSICAL CONSEQUENCES OF INHOMOGENEOUS GLASS STRUCTURE FROM SCATTERED-LIGHT SPECTROSCOPY DATA

Micro-inhomogeneous glass structure is investigated on the basis of scattered light spectroscopy including both Rayleigh and Mandel'shtam-Brillouin scattering spectroscopies (RMBS) and Raman scattering spectroscopy (RS). The Na2OB2O3, Na2OSiO2, R2OGeO2, RFGeO2 (R = Na, K) glass systems are examined. RMBS spectra include the Rayleigh scattering component at the incident light frequency, ν, the intensity of which is determined with the "frozen-in" density and concentration fluctuations and Mandel'shtam-Brillouin scattering components shifted by ± Δν the intensities of which are determined by "non-frozen" density fluctuations. Glass composition relationships of spectral intensity components (Landau-Placzek ratio), RL-P = IRayl./2IM-B, characterizing changes in micro-inhomogeneous structure with composition are calculated. Glass composition areas with maximum and minimum homogeneity are defined and their connection with miscibility gaps is established. Introduction of doped ions into the glasses is shown to lead to their selective entrance into fluctuation matrix micro-inhomogeneities enriched with alkali ions (segregation of doped ions) that causes an increase of Rayleigh scattering in doped glasses. In the spectral region of 50-1500 cm-1 the measured RS spectra are related to identified fragments on the basis of which decomposition into components belonging to fixed stoichiometry groups (constant composition groups ≡ CCG) is made. Concentrations and partial properties of CCG are determined. CCG are regarded as true glass components. RMBS spectroscopy data are compared with RS spectral data. A correlation is established between glass composition relationships of RL-P and CCG concentrations: glasses with minimum Rayleigh scattering intensity have single-type CCG. "Frozen-in" concentration fluctuations defining Rayleigh scattering are attributed to CCG concentration fluctuations. © 1990.