Investigation of lithium chloride-lithium borate-tellurium dioxide glasses : an example of complex anionic speciation

Abstract

Glasses in the system lithium chloride-lithium borate-tellurium dioxide have been prepared by the melt quenching route and characterised for their densities, glass transition temperatures and heat capacities. Their structures have been investigated using infrared, Raman and magic angle spinning nuclear magnetic resonance spectroscopies. While the structure consists of trigonal and tetrahedral borate groups, the tetrahedral boron in these glasses reaches much higher concentrations than in binary borate glasses. Tellurite species are present in both trigonal bipyramidal and trigonal pyramidal structures. The actual concentrations of the two borate and two tellurite species are interdependent. Their concentrations are also influenced by LiCl in the glass. The nature of speciation and chemical origin of the equilibration of the various species is examined using a structural model. The model has been used to rationalise the variation of the different properties in the glass system.