Effect of Bi 2O 3 on EPR, optical transmission and DC conductivity of vanadyl doped alkali bismuth borate glasses

Abstract

Glasses with composition xBi 2O 3·(30− x)M 2O·70B 2O 3 (M=Li, Na) containing 2 mol% V 2O 5 have been prepared over the range 0≤ x≤15 ( x is in mol%). The electron paramagnetic resonance spectra of VO 2+ 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, α 2 and γ 2, have been calculated by recording the optical transmission spectra. In xBi 2O 3·(30− x)Li 2O·70B 2O 3 glasses there is decrease in the tetragonality of the V 4+O 6 complex for x up to 6 mol% whereas for x≥6 mol%, tetragonality increases. In xBi 2O 3·(30− x)Na 2O·70B 2O 3 glasses there is increase in the tetragonality of the V 4+O 6 complex with increasing x. The 3d xy orbit expands with increase in Bi 2O 3:M 2O ratio. Values of the theoretical optical basicity, Λ th, 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 Bi 2O 3:M 2O ratio.