Effect of Bi2O3 on EPR, optical transmission and DC conductivity of vanadyl doped alkali bismuth borate glasses Original Research Article

Glasses with composition xBi2O3·(30−x)M2O·70B2O3 (M=Li, Na) containing 2 mol% V2O5 have been prepared over the range 0≤x≤15 (x is in mol%). The electron paramagnetic resonance spectra of VO2+ of these glasses have been recorded in the X-band (≈9.3 GHz) at room temperature (RT≈300 K). Spin Hamiltonian parameters, g∥, g⊥, A∥, A⊥, dipolar hyperfine coupling parameter, P, and Fermi contact interaction parameter, K, have been calculated. The molecular orbital coefficients, α2 and γ2, have been calculated by recording the optical transmission spectra. In xBi2O3·(30−x)Li2O·70B2O3 glasses there is decrease in the tetragonality of the V4+O6 complex for x up to 6 mol% whereas for x≥6 mol%, tetragonality increases. In xBi2O3·(30−x)Na2O·70B2O3 glasses there is increase in the tetragonality of the V4+O6 complex with increasing x. The 3dxy orbit expands with increase in Bi2O3:M2O ratio. Values of the theoretical optical basicity, Λth, have also been reported. The DC conductivity increases with increase in temperature. The order of conductivity is 10−5 ohm−1 m−1 at low temperature and 10−3 ohm−1 m−1 at high temperature. The DC conductivity decreases and the activation energy increases with increase in Bi2O3:M2O ratio.