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The room temperature electron paramagnetic resonance (EPR) and optical absorption studies of PbO-Li2O-As2O3-B2O3 glasses have been done by introducing a transition metal ion Cu+2 ion as a spin probe with fixed mole% in the given glass composition. Glasses containing transition metal (TM) ion give the information of site symmetry around the Cu+2 ion of the host glass. The EPR spectra of Cu+2 in all glass samples recorded in the X-band frequency (9.1–9.7 GHz) have similar features. The spin-Hamiltonian parameters have been calculated; the observed values are g|| > g⊥ > ge and A|| > A⊥. It suggests that the site symmetry around Cu+2 ion is tetragonal distorted octahedral and the ground state of Cu+2 is dx2-y2 (2B1g) orbital. The Cu+2 ion is coordinated with six ligand atoms in a distorted octahedron site symmetry. The optical absorption spectra exhibit a broadband corresponding to d-d transition bonds of Cu+2 ion. Calculated bonding parameters suggest the covalent nature of in-plane σ-bonding (α2) and pure ionic nature for out-of-plane (β2) and in-plane π-bonding (β12). This data is correlated with the theoretical optical basicity (Λth) values, and it is observed that the Γσ value increases whereas Γπ values decrease with increasing Λth.

Electron paramagnetic resonance studies of the xBi2O3−(30-x)Li2O-10AS2O3−58B2O3 (where x=5, 10, 15, 20 and 25 mol%) containing 2 mol% V2O5 as the paramagnetic probe were carried out at room temperature. These glasses were prepared using conventional melt quenching. The amorphous nature of the prepared glass samples was confirmed by x-ray diffraction studies. From the EPR spectra, the spin-Hamiltonian parameters (SHP) of VO2+ ions, dipolar hyperfine parameter (P) and Fermi contact interaction parameter (K), molecular orbital coefficients (α2 and γ2), the number of spins participating in the resonance (N), and susceptibility (χ) have been evaluated. From the spin-Hamiltonian parameters, it was concluded that the vanadyl ions exist as VO2+ ions in octahedral coordination with tetragonal compression with C4V symmetry and the ground state is dxy. Tetragonality (Δg||/Δg1) of V4+ ion sites exhibited nonlinear variation in the glass composition in all the glasses studied. Further, the theoretical optical basicity of the glasses has also been evaluated and it is observed that the changes in optical basicity values are in accordance with the changes in SHPs.

Copper doped Li2O-Bi2O3-As2O3-B2O3 glasses were prepared by the conventional melt quenching process. The room temperature Electron paramagnetic resonance (EPR) and Optical absorption studies of the present glasses were made by introducing copper ion (Cu2+) as the spin probe. All the glass samples of the EPR spectra recorded at 8-12GHz (X-band) frequencies have alike spectral features. The spin-Hamiltonian parameters were calculated. These values indicate that the ground state of Cu2+ ion is dx2- y2 and the site symmetry around copper ions is tetragonally distorted octahedral. The optical absorption spectra exhibited a broad band corresponding to the d-d transition bands of Cu2+ ion. By correlating the EPR and optical absorption spectral data, the nature of the in-plane σ bonding between Cu2+ ion and the ligands is estimated.

Arsenate-based alkali borotellurite glasses with the general formula xLi2O-(30−x)TeO2-10A2O3-60B2O3, where 5 ≤ x ≤ 25, were formulated by the conventional melt quenching technique. The glassy nature of the samples was confirming by X-ray diffraction measurements. The influence of Li2O content on the Fourier transform IR, optical, and thermal properties, density, and other related properties of the prepared glasses was studied. The results reveal that the density and molar volume decrease and the glass transition temperature increases with increasing Li2O content This can be attributed to the difference in the ionic radii of lithium and tellurium oxides. The variation in the indirect optical bandgap and band tail with Li2O content is discussed in relation to the glass structure. On the basis of the values obtained for α O 2 − , the optical basicity, and the interaction parameter, the present glasses were termed normal ionic (basic) glasses. Fourier transform IR spectroscopy of the present glasses revealed that the borate network is affected by the replacement of TeO2 by Li2O. It was found that the fraction of four-coordinate boron atoms decreases and the fraction of three-coordinate boron atoms increases with increasing Li2O content.