Effects of Increasing Tungsten on Structural, Elastic and Optical Properties of xWO3–(40−x)Ag2O–60Te2O Glass System

Abstract

Ternary tellurite glasses with composition of xWO3(40−x)Ag2O–60TeO2 (x = 0–40 mol%) have been prepared by melt-quenching method. Elastic and optical properties of the glass system were obtained by ultrasonic velocity measurements and UV–vis spectroscopy, respectively, while structural investigation was carried out by using Raman spectroscopy. The longitudinal and shear velocities, vL and vs showed large increase at x from 0 to 20 mol% before decrease with further addition of WO3. Independent longitudinal modulus CL and shear modulus μ bulk modulus Ke Young's modulus Y and Debye temperature θD showed similar behaviors to both velocities. The large increase of the elastic moduli at x from 0 to 20 mol% is suggested to be due to the increase in WO6 octahedral unit structure indicating the increase of bridging oxygen (BO) and formation of stronger Te–O–W bonds compared to Te–O–Te bonds. On the other hand, for x > 20 mol%, the decrease in the elastic moduli was due to the increase of non-bridging oxygen (NBO) as a result of formation of WO4 tetrahedral via breaking Te–O–W network. Further analysis by using bulk compression and ring deformation models showed a slight decrease in the ratio of ideal bulk modulus Kbc to the experimental bulk modulus Ke and average atomic ring size, l for x 20 mol%. Our analysis also indicates that limited ring deformation took place and the main compression mechanism in this glass system was mainly ideal isotropic compression. On the other hand, optical band gap Eopt showed small variation for x = 0–20 mol% but decreased upon higher WO3 content while refractive index n showed the opposite trend. This optical behavior is suggested to be related to the changes in cross link density and NBO concentration in the glass system.