Effect of alkaline earths on spectroscopic and structural properties of Cu2+ ions-doped lithium borate glasses

Alkaline earth lithium borate glasses with composition 15RO-25Li(2)O-(60-x)B2O3: xCuO (where R = Ca, Ba and x = 0, 0.4 and 0.8) were prepared by the conventional melt quenching technique. X-ray diffractograms confirm the amorphous nature of the glass samples. Spectroscopic studies such as optical absorption, EPR and FTIR were used to understand the effect of modifier oxide and CuO dopant in the glass matrix. From the optical absorption spectra the absorption band which is attributed to the 2B(1g) 2B(2g) characteristic transition of Cu2+ ions in the distorted octahedral sites. The cut-off wavelength (lambda(c)), optical band gap (E-opt), and Urbach energy (Delta E) were also determined. The average electronic polarizability of the oxide ion alpha(o2)-(E-opt), optical basicity Lambda(E-opt) and Yamashita-Kurosawa's interaction parameter A(E-opt) were also examined. From the EPR spectra the spin-Hamiltonian parameters are evaluated. The values of spin-Hamiltonian parameters indicate that the site symmetry around Cu2+ ions is tetragonally distorted octahedral. Using electron paramagnetic resonance (EPR) and optical absorption data, the molecular orbital coefficients alpha(2) and beta(2)(1) are calculated. The FTIR studies show that these glasses are made up of BO3 and BO4 units. The variation of optical and spectroscopic parameters was discussed in terms of the ionic radius of alkaline earth metal modifier. (C) 2015 Elsevier B.V. All rights reserved.