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

Abstract

Glasses with compositions xNb 2O 5·(30 − x)M 2O·69B 2O 3 (where M = Li, Na, K; x = 0, 4, 8 mol%) doped with 1 mol% V 2O 5 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 Nb 2O 5 on the structure of these glasses have been reported. The electron paramagnetic resonance spectra of VO 2+ 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 V 4+ ions which exist as VO 2+ ions in octahedral coordination with a tetragonal compression in the present glasses. The tetragonality of V 4+O 6 complex decreases with increasing concentration of Nb 2O 5. The 3d xy orbit contracts with increase in Nb 2O 5:M 2O ratio. Values of the theoretical optical basicity, Λ th, have also been reported.