Abstract
Silica borotellurite glasses with compositions SiO2][SiO2][SiO2]0.2}0.99{V2O5}0.01]1-z (Ni0)z (where z = 0.005,0.010,0.015,0.020 and 0.025 M fraction) had been prepared by conventional melt quenching technique. X-Ray Diffractograms spectra confirm the amorphous nature of the prepared glasses. Study of infrared (IR) spectroscopy reveals an increase in the formation of nonbridging oxygens (NBOs) as nickel concentration increases. This resulted in the decrease of density and oxygen packing density (OPD) of the glass. The observed ESR spectra confirmed that V4+ ions exist as vanadyl ion in the octahedral coordination with tetragonal compression. Based on UV–vis absorption spectra, four absorption bands have been observed with indirect optical band gap, Urbach's energy, refractive index and other optical parameters have been calculated. The Ni2+ ions were distributed with octahedral and tetrahedral coordination of the ligand field. Nevertheless, the octahedral coordination of Ni2+ dominated over tetrahedral coordination with the increase of NiO concentration consequently, confirmed the increase in NBOs from the IR spectra. These observations reflect the decrease in optical band gap, metallization criterion and the increase in Urbach's energy and refractive index.
The FTIR spectra are characterized by four regions and a shoulder (400-600 cm−1, 600-800 cm−1, 800-1000 cm−1, 1000-1100 cm−1 and 1200-1400 cm−1), which normally consist of more than one peak. The bands are dominated by structural units of glass formers which are tellurite, borate and silicate networks. Most of the structural units of glass modifier are overlapped with the vibration bands of glass former networks.