A temperature-dependent Raman study of the xLiCl-(1-x)TeO2 glasses and melts

Raman scattering has been employed to study the temperature and composition dependence of the vibrational modes for the glass-forming oxyhalide mixtures xLiCl-(1-x)TeO2 (x=0, 0.2, 0.3, 0.35, 0.5 and 0.67) in the glassy, supercooled and liquid state up to 600 °C. The analysis has shown that the network structure of the glass/melt is formed by mixing trigonal bipyramid and trigonal pyramid units. The change of LiCl content and/or temperature results to conversion of the trigonal bipyramid to trigonal pyramid units with a varying number of non-bridging chlorine and oxygen atoms. The fraction of the terminal oxygen atoms doubly bonded to tellurium versus temperature has been directly estimated from the Raman spectroscopic results with the aid of a structural model concerning the tellurite network systems. A well-resolved Boson peak (BP) dominates the low-frequency Raman spectra. The temperature dependence of the maximum of the BP has also been determined and discussed in the framework of its microscopic origin.