EPR and DSC studies on MgO-R2O-B2O3-V2O5 alkali glasses

EPR and DSC studies were carried out on MgO-R2O-B2O3-V2O5 glasses. The electron paramagnetic resonance spectra of V4+ ion in the ternary glass system xMgO-(30-x)R2O-70B(2)O(3) (R = Li, Na, K) were recorded at X-band frequencies at 303 K. The V4+ ions in the present glass system exists as VO2+ ions in octahedral coordination with tetragonal compression. The site symmetry of vanadyl is C-4v and the ground state of 3d(1) ion is d(xy). Tetragonality (Delta g(parallel to)/Delta g(perpendicular to)) of V4+ ion sites show a nonlinear variation with MgO content in the glasses. The covalency rates indicate moderate covalency for sigma and pi-bonds. The optical basicity values were also reported. Glass transition temperatures (T-g) of the glasses were found to increase linearly with increasing MgO content.