Impact of heavy lead oxide on structural, optical and ligand field properties of B2O3–Na2O–NiO glass matrix

Herein, a nickel-doped borate glass system, with variable additions of lead oxide, was prepared by melting and air quenching method. The impact of heavy lead oxide on structure, optical, electronic transitions, ligand field and nonlinear optical features was investigated. The glass structure was scrutinized by XRD, indicating the amorphousness of the current glass. The measured and empirical densities increased with lead oxide additions, indicating the densification of the network, while comparing both densities confirms the randomness of the glass network. Infrared spectra confirmed the deteriorated existence of non-bridging oxygen (NBO) bonds and the high ability of lead oxide to modify the glass network and form different structural units such as Pb . The current optical studies revealed the existence of ions in octahedral coordination, with high optical activity within some of the optronic transitions that were observed in visible and infrared regions. Among these optronic transitions, the transitions at 429, 524, 805 and 1222 nm were exploited using a Gaussian deconvolution process to determine the splitting energy and Racah parameters. Bewitchingly, the splitting energy increased; meanwhile, the Racah B and C parameters decreased, indicating that the lead addition increased the ligand- ions interaction energy and decreased the internal electronic interactions inside d-orbitals of ions. As a result of these interactions, the covalent bonding nature increased. Furthermore, lead oxide additions push the glass edges toward low energy, mitigating the optical band gaps from 3.41 eV to 2.92 eV, while Urbach energy increased due to enhanced amorphousness. Due to the higher polarizability of lead ions, the linear and non-linear optical properties of current glasses are enhanced.