Spectroscopic studies of Cu2+ spin probe in sodium niobium based tellurite glasses

Abstract

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 (T_g) 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 d_{x2- 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.