Short and medium range order in ternary borate glasses

Abstract

Low frequency Raman scattering experiments are described in ternary lithium borate glasses (B 2O 3-0.6 Li 2O yLi n X with n = 1, X = F, Cl, Br and I; or n = 2, X = SO 4). The ‘boson peak’ is analyzed in terms of a correlation length of phonon propagation and of a phonon-photon coupling. The concentration and the chemical composition dependance of the sound velocity, as well those of the structural correlation length deduced from the Raman spectra are discussed. Using a linear dependance for the coupling parameter, the experimental density of vibrational states is obtained and compared with those calculated in binary lithium borate glasses. Two different structural modifications depending on the nature of the anions of the ‘doping salt’ (halide or sulfate ions) are proposed to describe the glass network conformation.