Electron paramagnetic resonance and optical properties of Cu+2 in PbO-Li2O-As2O3-B2O3 glasses

Abstract

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.