Structural and electronic properties of tellurite glasses

The structural properties of some tellurite glasses were investigated by FT-IR spectroscopy, density measurements, and quantum chemical calculations. Main results reveal that the ratio TeO₄/TeO₃ is found to decrease in the order V₂O₅ > B₂O₃ > P₂O₅. For borate–tellurate glasses, the Van Hove singularities corresponding to Te 5s orbital-derived states are cleft suggesting that there are strong tellurium–oxygen interactions. On the other hand, a strong effect of TeO₂ on the vitreous B₂O₃ network is also demonstrated by FT-IR spectrum. This effect yields the apparition of small peaks in the region ranges between 800 and 1600 cm⁻¹ and probably the partial crystallization of the sample. Its spectral features are due to the B–O bond stretching of [BO₄] and [BO₃] structural units. The quantum chemical data obtained by us show that phosphate–tellurite and vanado–tellurate glasses can behave as semiconductors, whereas borate–tellurite glasses as insulators because the gap between the valence and conduction bands is >3 eV.