Structural investigation of the xV2O5(1-X)[Bi2O3•B2O3] glasses by IR absorbtion, EPR and NMR

The aim of structural characterization of the V2O5 - Bi2O3 - B2O3 glassy system is to clarify the role played by the Bi2O3 as an unconventional network former in the structure of the investigated samples. FT-IR absorption spectra present the vibration frequencies characteristic to the both Bi2O3 and B2O3, and, also, the influence of vanadium penthaoxide on the main IR absorption bands. The presence of the main structural units [Bi3O], [BiO6], [BO3] and [BO4] and their dependence on the V2O5 content is evidenced. The EPR (Electron Paramagnetic Resonance) spectra contain a single resonance line centered at g approximate to 1.98 with a partially resolved V-51 (I=7/2) hyperfine structure for the samples with high V2O5 content (x > 30 mol %). This fact reveals the existence of the isolated paramagnetic V4+ ions, whose resonance line overlaps the broad line characteristic to the associated V4+ ions (for 1 <= x <= 20 mol %). 11 B MAS-NMR (Magic Angle Spinning Nuclear Magnetic Resonance) spectra performed on the studied glass samples indicate the changes produced by the addition of vanadium penthaoxide on the coordination of boron atoms. The modification of the relative intensity and position of the resonance lines corresponding to the boron atoms suggests the influence of V2O5 on the local structure of the studied glasses.