Effect of CdO on physical and optical properties of cadmium silicon bismuthate glasses

Glasses with composition x CdO. y SiO 2 . y Bi 2 O 3 (with x=0, y=50; x=10, y=45; x=20, y=40 and x=30, y=35 mol %) were synthesized using conventional melt quenching technique. The variation in physical and optical properties has been studied as a function of CdO content in cadmium silicon bismuthate glasses. The amorphous nature was confirmed by X- ray diffraction. The changes in physical properties like density, molar volume, oxygen packing density (OPD) and crystalline volume (V c ) shows structural modification on addition of CdO. Thermal properties like glass transition temperature (T g ) and crystallization temperature (T p ) were determined by differential scanning calorimetry (DSC) and values of T g were found to increase while that of T p decrease as substitution of CdO increases. The fundamental absorption edge has been found out from the optical absorption spectra. The optical band gap, E g , for indirect allowed transitions has been determined and its value lies between 2.70-2.76 eV and found to decrease with increase in CdO content. The systematic study of structure was carried out by Infrared and Raman spectroscopy which shows that these glasses are made of [BiO 3 ], [BiO 6 ] and [SiO 4 ] structural units and both symmetric as well as asymmetric stretched vibrations of Si-O bonds in SiO 4 were present