Thermal and optical characterization of Ge xSn 10 Se 90-x (x = 14, 18, 22, 26) glasses has been carried out using differential scanning calorimetry and UV-VIS-NIR spectroscopy, respectively. Bulk samples were prepared using conventional melt quenching technique. Amorphous nature of the prepared samples was confirmed using X-ray diffraction. The transmission spectra of as deposited films, for normal incidence, were recorded in the range 400-2,500 nm. Optical constants such as absorption coefficient, refractive index and extinction coefficients have been determined using the envelope method. Dispersion of refractive index has been analyzed using singleeffective oscillator model. Optical band gap has been measured using Tauc plots. Effect of composition variation on thermal and optical properties has been discussed in view of chemical bond approach.

In the current studies optical, physical and structural properties of rare-earth doped borate glasses have been reported. Bulk samples were prepared by using melt quenching technique with nominal composition 70B2O3-(17-x)ZnO-10PbF2-3Na2O-xDyF3 and 60B2O3-(27-x)ZnO-10PbF2-3Na2O-xDyF3, where (x=0,1). XRD analysis was used to confirm the amorphous nature of prepared samples. Optical and structural properties of as prepared samples were studied using UV-Visible and FTIR absorption spectra. The undoped and doped glasses exhibit characteristic absorption bands due to the presence of rare earth ion. A decrease in the band gap has been observed with the addition of rare earth ion. Variations in density have been observed with the addition of rare earth ion.

The electrical conductivity of doped ZnS with different impurities (Mn, Fe, Co, Ni and Cu) of various concentrations has been measured to verify the existence of ladderlike levels of 'killers' of luminescence. Attempts have been made to ascertain the separation between-the valence band of the host ZnS and the ground state of the accepter impurities and also to investigate the effect of various concentrations of impurities on the electrical conductivity of doped ZnS.

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