Solid state MAS NMR Investigation on the Local Structures of_xV₂O₅-B₂O₃-_yNa₂O Glasses

Abstract

The local structures of the boron and vanadium sites in the ternary glass xV2O5-B2O3-yNa2O were studied by 11 B and 51 V magic angle spinning (MAS) nuclear magnetic resonance (NMR). With increasing x, the mole ratios of the BO3 and BO4 structures were enhanced, as were the quadrupole asymmetry parameters for the BO3 structures, while the quadrupole coupling constants for the sites were reduced. However, the opposite trends were observed with increasing y, implying that V2O5 and Na2O play opposite roles. The VO4, VO5 and VO6 structures with all oxygens bonded to the vanadium neighbors were identified. Vanadiums bonded to the greater number of oxygens were more populated at higher contents of Na2O and V2O5. In addition, the VO4 structures with at least one oxygen bonded to boron instead of vanadium were detected at low Na2O contents. The electron densities of various vanadium oxide structures were affected by the weight densities and vanadium ion densities. The VO4 structures were more likely to be vanadium oxide structures right next to V 4+ ions.