Spectroscopic studies of Cu2+ spin probe in sodium niobium based tellurite glasses
Differential scanning calorimetry (DSC), electron spin resonance (ESR), Raman, infrared (IR) and optical absorption studies on 10Na2O-xNb2O5-(89-x)TeO2-1CuO glasses (where x =0, 5, 10, 15 and 20 mol%) containing Cu2+ spin probe have been carried out. Glass transition temperature (Tg) and thermal stability of glass samples have been estimated from the DSC measurements and it has been found that both increase with increasing the Nb2O5 content. From Raman and IR spectra, it is clear that present glass system consists of structural units of TeO3 (tp) and TeO4 (tbp) and NbO6 octahedra. Also, TeO4 units convert into TeO3 units with change in Nb2O5 content. The hyperfine splittings in the parallel features of ESR spectra of Cu2+ are recorded for all compositions. ESR results show that g|| > g indicating that the Cu2+ ion is in tetragonal distorted octahedral site and its ground state is dx2- y2. There is considerable variation in Hamiltonian parameters for the different compositions. The observed optical absorption peak of Cu2+ is found to be maximum at 780 nm for 10 mol% of Nb2O5 content. Bonding parameters and % bonding symmetry are calculated from both optical and ESR data changing with increasing Nb2O5 content.
Tellurite glasses, ESR, IR, Raman and Optical absorption spectra
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