Influence of the La2O3 addition on the structure and optical features of La2O3–NiO–BaO–B2O3 glass

Abstract

The influence of the La2O3 addition on the microstructure, linear and nonlinear optical parameters of nickel borate glass was carefully investigated for the La2O3–NiO–BaO–B2O3 system. The La2O3 content of the present glass was varied from 0.0 to 10.0 mol%, while the glass modifiers of BaO and glass intermediate of NiO were fixed at 19 and 1.5 mol%, respectively. Based on the structural investigations, the bond density remarkably increased from 7.37 × 1019m−3 to 8.66 × 1019m−3 by a ratio of 18 % with increasing La2O3/B2O3 ratios. Additionally, the presence of Ni2+ ions as NiO6 units was confirmed by the brown shade originating from the absorption band observed at 427 nm in the optical absorbance of the studied glass. Furthermore, the Ni3+ ions do not play a role in the coloring of the glass. Moreover, the fundamental absorption edges of the glass shift towards lower energy values with increasing La2O3 concentrations, confirming the decreased behavior of the band gaps. Moreover, the linear and nonlinear refractive indices increase with increasing of La2O3 concentrations. Additionally, the ligand field characteristics of Ni cations, such as the ligand field splitting parameter and Racah parameter, exhibit opposite behaviors upon introducing additional La2O3 content. A decrease in values of the ligand field splitting, while the Racah parameters exhibit increased values. The observed outcomes demonstrate a tendency of the bonds connecting the Ni ions and their ligands to possess higher degrees of ionic nature. Based on the results, the present glass samples can function as solar thermal collectors by collecting sunlight and utilizing it for direct heating and indirect electrical power generation.