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 (1.1Tg), 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 1.3Tg), whereas it leads to the formation of the new crystalline phase TeVO4 during heating to 725 K (1.4Tg). We discuss the origin of these two phenomena by considering the changes both in glass structure and in the redox reaction.