EPR and optical properties of alkali halo cadmium borate glasses containing vanadium ions

摘要

The glass composition x NaF-(40-x) CdO-58B_2O_3-2V_2O_5 with (x=5, 10, 15, 20, 25, 30 & 35 mole %) have been prepared by melt quenching technique. Glasses are characterized by XRD, EPR and UV-Visible spectra. No characteristic peaks are found in XRD spectra revealing the amorphous nature of prepared glasses. Spin-Hamiltonian parameters g_∥, g_┴, A_∥, A_┴, bonding parameters (1-α~2), (1-γ~2), Fermi contact interaction parameter (K), dipolar hyperfine coupling parameter (P), number of spins (N) and paramagnetic susceptibility (χ) were calculated. It was observed that these parameters are varying nonlinearly with increasing NaF concentration. From the spin Hamiltonian parameters it is confirmed that vanadium ions exist as VO~(2+) ions with octahedral co-ordination with tetragonal compression with C_(4V) symmetry and the ground state is being d_(xy). Optical absorption spectra of VO~(2+) ions in the present glass samples had shown two transitions correspond to ~2B_(2g)→~2B_(1g), ~2B_(2g)→~2E_g. Optical band gap, Urbach energy and refractive index values are varying non-linearly with increasing NaF concentration.