Inhomogeneous structure of inorganic glasses studied by Rayleigh, Mandel'shtam-Brillouin, Raman scattering spectroscopy, and acoustic methods

Abstract

General features of inhomogeneous structure characteristic of inorganic glasses are analyzed on the base of results of combined application of light scattering spectroscopy and high temperature acoustic methods. In the framework of the model of "freezing" equilibrium thermodynamic fluctuations of melt the glass composition dependences of Landau-Placzek ratios taken from Rayleigh and Mandel'shtam-Brillouin scattering (RMBS) spectra and high temperature acoustics data for glass melts make it possible to estimate separately the relative role of "frozen-in" density and concentration fluctuations in the intensity of Rayleigh scattering (RS) by glasses. The obtained data opens the way to elaboration of glasses of the highest chemical and/or optical homogeneity for fiber and laser optics. It was found that Rayleigh scattering is sensitive to the selective entering of doped ions into concentration fluctuations of a glass host (the so-called dopant segregation phenomenon). Thus, RMBS data allows controlling the real dopant-dopant separations in glasses that are significant for the elaboration of laser glasses. Being carefully measured, the intensities of Raman scattering spectral bands can be used for the determination of concentrations and partial properties of constant stoichiometry groups (CSG) from which some binary glass forming systems are built. Comparison of RMBS and Raman scattering data leads to the conclusion that concentration fluctuations in some binary glass forming systems can be considered as fluctuations of CSGs. The result can be used for the elaboration of EO glasses with minimized RS losses.