Structural investigation and electron paramagnetic resonance of vanadyl doped alkali niobium borate glasses

Glasses with compositions xNb2O5·(30 − x)M2O·69B2O3 (where M = Li, Na, K; x = 0, 4, 8 mol%) doped with 1 mol% V2O5 have been prepared using normal melt quench technique. The IR transmission spectra of the glasses have been studied over the range 400–4000 cm−1. The changes caused by the addition of Nb2O5 on the structure of these glasses have been reported. The electron paramagnetic resonance spectra of VO2+ ions in these glasses have been recorded in X-band (9.14 GHz) at room temperature (300 K). 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) due to V4+ ions which exist as VO2+ ions in octahedral coordination with a tetragonal compression in the present glasses. The tetragonality of V4+O6 complex decreases with increasing concentration of Nb2O5. The 3dxy orbit contracts with increase in Nb2O5:M2O ratio. Values of the theoretical optical basicity, Λth, have also been reported.