Vibrational, Optical and EPR studies of TeO2-Nb2O5-Al2O3-V2O5 glass system doped with vanadium

Tellurium niobate glasses containing aluminum oxide have been prepared from the conventional melt quenching technique. Optical band gap (Eopt), Urbach energy (ΔE), refractive index (n), optical basicity (Ʌ), and electronic polarizability (α) were determined from optical absorption data. Variation in the network configuration is studied by Fourier transform infrared (FTIR) and Raman spectroscopy measurements. From FTIR and Raman studies it is clear that the glass consists of [TeO3] and [TeO4] and [NbO6] structural units. The glass transition temperature (Tg) of the glasses are studied by Differential scanning calorimetry (DSC). Increase in the glass transition temperature (Tg) with increase in the Nb2O5 is observed. The Spin Hamiltonian parameters of VO2+ ions showed a linear decrease with increase in the Nb2O5. EPR results suggest that VO2+ occupies octahedral site with tetrahedral compression. From optical, structural and thermal studies it is clear that the variation in the niobium content in the glass does affect the structural arrangement of atoms inside the glass network and also enhance the optical properties.