Impact of silicon doping on the structure and crystallization of a vanadium-tellurite glass

We studied the effect of silicon doping on the structure and crystallization behavior of 50V₂O₅-50TeO₂ (mol%) (VT) glass by performing solid-state nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). We observed two interesting phenomena. First, when the mixture of glass and Si is heated in argon to 560 K (1.1T_g), Si starts to react with VT glass and is oxidized to amorphous silica, being confirmed by NMR and FTIR. Second, Si suppresses the formation of the Te₂V₂O₉ phase in VT glass during heating process up to 650 K (about 1.3T_g), whereas it leads to the formation of the new crystalline phase TeVO₄ during heating to 725 K (1.4T_g). We discuss the origin of these two phenomena by considering the changes both in glass structure and in the redox reaction.