ESR, optical absorption, IR and Raman studies of xTeO2 + (70 − x)B2O3 + 5TiO2 + 24R2O:1CuO (x = 10, 35 and 60 mol%; R = Li, Na and K) quaternary glass system

xTeO2 + (70 − x)B2O3 + 5TiO2 + 24R2O:1CuO (x = 10, 35 and 60; R = Li, Na and K) glass system were studied by spectroscopic techniques such as ESR, optical absorption, Raman and IR. From ESR spectra, the spin Hamiltonian parameter values indicate that the ground state of Cu2+ is dx2−y2dx2−y2 and the site symmetry around the Cu2+ ion is tetragonally distorted octahedral coordination. Bonding parameters calculated from optical absorption and ESR data are found to change with alkali oxide and TeO2 content. Bonding parameters indicate a slight covalency for the in-plane σ bonding as compared to in-plane and out-of-plane π bonds. Both Raman and IR results show that glass network consists of TeO3, TeO4, BO3, BO4 and RiO4 group as basic structural groups. BO3–BO4− ring structure interconnected by TeO3− and TeO4− groups, where the BO4− groups are neighbors of the TeO3− groups. BO3 → BO4 transition is also observed, which correlates with the transition of TeO4 → TeO3 via TeO3+1.

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► Peak of Cu2+ is found to be maximum at around 794 nm for lithium boro tellurite glasses.
► Variation in g|| and A|| values is due to change in environment of Cu2+ ion due to the structural change in the glass.
► BO3–BO4− ring structure is interconnected by TeO3− and TeO4− groups, where the BO4− groups are neighbors of TeO3−groups.
► The structure comprising, isolate a BO3−, B2O5, BO4−, and metaborates, which enables glass forming for Borate rich glasses.
► Distorted TeO4/2 network with BO3−–BO4− ring structure and TeO3− group is enables glass forming for tellurite rich glasses.