Effect of V2O5 on structural and elastic properties of alkali silicate SiO2–Na2O–NaF glasses

A series of V ₂O ₅–doped alkali silicate SiO ₂–Na ₂O–NaF glasses were prepared by the melt quenching technique. Amorphousness of the samples was characterized using powder X-Ray diffraction (XRD) analysis; and the structural role of V ₂O ₅, Na ₂O and NaF in the silicate network was explored using Fourier Transform Infrared (FTIR) spectroscopy. Elastic properties, determined by using ultrasonic technique, were correlated with the compositional and structural parameters as well as the excess molar volume. The substitution of SiO ₂ by Na ₂O and NaF in the base SiO ₂–Na ₂O–NaF glass resulted in the breaking of Si–O–Si linkages and creation of NBOs, whereas the addition of V ₂O ₅ resulted in formation of VO ₅ structural units and weak V–O–V and Si–O–V linkages. Makishima-Mackenzie`s theory is valid for pure SiO ₂ and V ₂O ₅–free glasses. The discrepancy between theoretical and observed elastic moduli and micro-hardness of V ₂O ₅–doped glasses was discussed in details.