Boron and pentavalent vanadium local environments in binary vanadium borate glasses

Vanadium borate glasses containing 5 to 25%mol vanadium oxide (V2O5) were investigated. Prepared via the melt-quench technique, these glasses were examined by Fourier transform infrared, Raman, ultraviolet-visible and synchrotron-based X-ray absorption spectroscopy. Ultraviolet-visible and X-ray absorption spectra reveal that the only oxidation state of vanadium ions found in these glasses is 5 +. Further result shows a subsequent increase in the molar volume of glass as V2O5 rises. This observed relationship indicates the presence of large boron-oxygen frameworks, including loose diborate and pyroborate units, confirmed by Fourier transform infrared and Raman spectra. Non-bridging oxygens of boron network are also formed in all glasses. Moreover, it is found that while four- and five-fold coordinated vanadium are present in all glasses, only five-fold coordinated vanadium show a significant increase following a rise in vanadium content.