Structural, thermal and optical properties of TeO2-ZnO-CdO-BaO glasses doped with VO2+

The glasses with composition 64TeO(2)-15ZnO-(20-x)CdO-xBaO-1V(2)O(5) (0 <= x <= 20 mol%) were prepared by conventional melt quenching technique. X-ray diffraction analysis was used to confirm the amorphous nature of the glasses. The optical absorption studies revealed that the cut-off wavelength (lambda(alpha)) decreases while optical band gap energy (E-opt) and Urbach energy (Delta E) values increase with an increase of BaO content. Refractive index (n) evaluated from E-opt was found to decrease with an increase of BaO content. The physical parameters such as density (rho), molar volume (V-m), oxygen packing density (OPD), optical basicity (Lambda), molar refraction (R-m), and metallization criterion (M) evaluated and discussed. FTIR and Raman spectroscopic studies showed that the glass network consists of TeO4, TeO3+1/TeO3 and ZnO4 units as basic structural units. The glass transition temperature (T-g) of glass sample, onset crystallization temperature (T-o) and thermal stability Delta T were determined from Differential Scanning Calorimetry (DSC). Using electron paramagnetic resonance (EPR) spectra of vanadium glasses the spin Hamiltonian parameters and dipolar hyperfine coupling parameters of VO2+ ions were calculated. It was found that V4+ ions in these glasses exist as VO2+ in octahedral coordination with a tetragonal distortion and have C-4v symmetry with ground state d(xy). Tetragonality (Delta g(vertical bar vertical bar)/Delta g(perpendicular to)) of vanadium ion sites exhibited non-linear variation with BaO content. (C) 2015 Elsevier B.V. All rights reserved.