High-T-g GeS2 based glasses for chemical sensing applications

Chalcogenide glasses based on the GeS2-Ga2S3-CsI system have been engineered for high temperature optical fibres operating above 150 A degrees C in chemical process environments. The glass structure has been modified to enhance the glass transition temperatures (T (g)) from 350 to 450 A degrees C, leaving a clear margin of 200 A degrees C at which the structural relaxation is likely to be insignificantly small for contributing to structural damage to the fibre. We have systematically carried out the Raman spectroscopy at 514 nm for analysis of the structural changes as a function of composition. The Raman spectroscopic analysis is also complemented by the Infrared (IR) transmission spectroscopy for the characterisation of likely vibrational modes. The glass compositions were also analysed for their devitrification and near T (g) relaxation behaviour. On the basis of the devitrification characteristics we have also characterised the thermal stabilities of various GeS2-Ga2S3-CsI modified glasses. The structural relaxation behaviour above the T (g) was also characterised using a differential mechanical analyser by measuring the viscosity (eta).