STRUCTURAL STUDIES OF TUNGSTATE TELLURITE GLASSES BY RAMAN-SPECTROSCOPY AND DIFFERENTIAL SCANNING CALORIMETRY

Raman spectroscopy and differential scanning calorimetry (DSC) are used in this work to study lattice structures, crystallization behavior, effects of heat treatment and the thermal properties of a wide range of tungstate-tellurite glasses {(100 - x)TeO2 + xWO(3)} with 5 less than or equal to x less than or equal to 50 mol%. We extended the glass formation range of this glass system up to 50 mol% of WO3 using a platinum crucible. The Raman vibrational bands and the different coordination states of the constituent oxides are discussed. Interesting aspects of Raman spectra and DSC were found, and this gives integrated information about the short-range order of the structures of these glasses as a function of WO3 concentration. The thermal parameters, such as the glass transition temperature (T-g), the onset of crystallization temperature (T-o), and the heat of crystallization delta H were determined. The relation In T-g = 1.6Z + 2.3, where Z is some average coordination number of the constituent atoms, known for molecular and chalcogenide glasses, was found to be satisfied by these oxide glasses up to a certain threshold (27.5 mol%) of WO3.