Effect of WO3 on EPR, structure and electrical conductivity of vanadyl doped WO3 center dot M2O center dot B2O3 (M=Li, Na) glasses

Glasses with composition xWO(3) center dot (30-x)M2O center dot 70B(2)O(3) (M=Li, Na; 0 <= x <= 15) doped with 2 mol% V2O5 have been prepared using the melt-quench technique. The electron paramagnetic resonance spectra have been recorded in X-band (v approximate to 9.14 GHz) at room temperature (RT). The spin Hamiltonian parameters, dipolar hyperfine coupling parameter and Fermi contact interaction parameter have been calculated. It is observed that the resultant resonance spectra contain hyperfine structures (hfs) only due to V4+ ions, which exist as VO2+ ions in octahedral coordination with a tetragonal compression in the present glass system. The tetragonality increases with WO3:M2O ratio and also there is an expansion of 3d(xy) orbit of unpaired electron in the vanadium ion. The study of IR transmission spectra over a range 400-4000 cm(-1) depicts the presence of WO6 group. The DC conductivity (sigma) has been measured in the temperature range 423-623 K and is found to be predominantly ionic