Study of electron paramagnetic resonance, optical transmission and dc conductivity of vanadyl doped Bi2O3•B2O3•Li2O glasses

Glasses with composition xBi2O3.(70-x)B(2)O(3)(.)30Li(2)O containing 2 mol% V2O5 have been prepared over the range 0less than or equal toxless than or equal to20 (in mol%). The electron paramagnetic resonance (EPR) spectra of VO2+ ions of these glasses have been recorded in the X-band (approximate to9.13 GHz) at room temperature. Spin Hamiltonian parameters (SHP), g(parallel to), g(perpendicular to), A(parallel to), A(perpendicular to), dipolar hyperfine coupling parameter, P, and Fermi contact interaction parameter. K, have been calculated. The molecular orbital coefficients, alpha(2) and gamma(2), have been calculated by recording the optical transmission spectra in the wavelength range of 500-850 nm. It has been observed that the octahedral symmetry around V4+ ion is improved, and the 3d(xy) orbit of the unpaired electron of the vanadium ion expands with increase in Bi2O3:B2O3 ratio. Values of the theoretical optical basicity, Lambda(th), have also been reported. The dc conductivity increases with an increase in temperature. The dc conductivity variation with Bi2O3 content shows mixed glass-former effect at x = 8 mol%. For x = 10 mol%, the conductivity decreases with increase in Bi2O3 content because of the decrease in the mobility and the number of Li+ ions available for the conduction. (C) 2004 Elsevier B.V. All rights reserved.