Structural properties of alumina-doped lithium borovanadate glasses and glass-ceramics

Abstract This study elucidates the role of Al2O3 in the lithium borovanadate (LBV) system, Li2O-B2O3-V2O5, in improving the glass-forming region of LBV glass. This increased glass-forming tendency is likely due to formation of [AlO4]− units. 11B, 27Al, and 51V nuclear magnetic resonance measurements suggest an importance of V-O-Al linkages and distribution of Li for charge compensation of [AlO4]− and [BO4]− units. Intense 51V NMR signals and resolved hyperfine coupling patterns in the electron paramagnetic resonance (EPR) spectra indicate that the majority of vanadium is pentavalent (V5+) and minor amounts of paramagnetic vanadium (V4+) are present. The EPR interaction parameters suggest that the vanadyl-like environments can be described as tetragonally compressed distorted octahedra. Based on V-2p3/2 X-ray photoelectron spectroscopy, the V4+ concentration is estimated at