Electron paramagnetic resonance study of vanadium doped lead haloborate glasses

Electron paramagnetic resonance studies of the lead haloborate glass system xPbX-(30-x)PbO-68B(2)O(3) (X=F-2, Cl-2, Br-2 and x=5, 10, 15, 20 and 25 mol%) containing 2 mol% V2O5 as the paramagnetic probe were carried out at room temperature. These glasses were prepared using conventional melt quenching. The amorphous nature of the prepared glass samples was confirmed by x-ray diffraction studies. The EPR spectra were recorded at X-band frequencies with 100 kHz frequency modulation at room temperature. The spin-Hamiltonian parameters (SHP) of VO2+ ions, dipolar hyperfine parameter (P) and Fermi contact interaction parameter (K), molecular orbital coefficients (alpha(2) and gamma(2)), the number of spins participating in the resonance (N), and susceptibility (x) have been evaluated. From the spin-Hamiltonian parameters it was observed that g(parallel to)A(perpendicular to). From these results it was concluded that the vanadyl ions exist as VO2+ ions in octahedral coordination with tetragonal compression with C-4V symmetry and the ground state is d(xy). Tetragonality (Delta g(parallel to)/Delta g(perpendicular to)) of V4+ ion sites exhibited nonlinear variation with glass composition in all the glasses studied. This nonlinear variation might be due to changes in the ligand field at the site of V4+ ion, indicating variation in octahedral symmetry.