The effect of V2O5 on alkaline earth zinc borate glasses studied by EPR and optical absorption

10 wt% SrO:30 wt% ZnO:60 wt% B2O3 incorporated with different vanadyl concentrations were studied by means of electron paramagnetic resonance (EPR) and optical absorption techniques. The spin-Hamiltonian parameters (g and A), bonding parameters (alpha(2) and beta(center dot 2)(2)) and Fermi contact interaction parameter K have been calculated. The values of spin-Hamiltonian parameters indicate that the VO2+ ions in strontium zinc borate glasses were present in octahedral sites with tetragonal compression. The spin concentration (N) participating in resonance was calculated as a function of temperature (93-273 K) for strontium zinc borate glass sample containing 0.9 wt% of VO2+ ions and the activation energy (E-a) was calculated. From the EPR data, the paramagnetic susceptibility (chi) was calculated at various temperatures and the Curie constant (C) was evaluated from the 1/chi-T graph. The optical absorption spectra of VO2+ ions in these glasses show two bands corresponding to the transitions B-2(2g) -> B-2(1g) and B-2(2g) -> E-2(g) in the order of decreasing energy respectively. The optical band gap energies (E-opt) and Urbach energy (Delta E) have been determined from their ultraviolet edges. The theoretical values of optical basicity (Lambda(th)) of these glasses have also been evaluated. (C) 2011 Elsevier B.V. All rights reserved.