Spectroscopic properties of the V-doped borate glasses

Abstract

Electron paramagnetic resonance (EPR) and optical absorption spectra in borate glasses of Li2B4O7:V, LiKB4O7:V, CaB4O7:V, and LiCaBO3:V compositions with added 0.5 and 1.0 mol.% V2O5, were investigated. The EPR spectroscopy clearly shows that the V impurity is incorporated into the network of studied glasses, mainly, as isolated vanadyl (VO2+) molecular complex centres. Spin Hamiltonian parameters of axial symmetry (g||, g⊥, A||, A⊥), dipolar hyperfine coupling (P) and Fermi contact interaction (K) constants of the VO2+ centres in octahedral sites with a tetragonal compression (C4v local symmetry) for all investigated glasses were determined from their experimental EPR spectra. Optical absorption bands, observed in the investigated glasses have been identified and interpreted. Crystal field parameters (Dq, Ds, Dt) and molecular orbitals (bonding) coefficients (β⁎2, επ⁎2) for VO2+ centres in the studied glasses were calculated and compared with referenced data for other V-doped borate glasses with similar compositions.