Influence of SiO2 substitution on optical, nonlinear, and gamma-ray shielding properties of Ni2+-doped sodium borosilicate glasses

Understanding the composition–structure–property correlation in glasses is essential for tailoring their optical and radiation shielding performance. In this work, we introduce an investigation of nickel-doped sodium borosilicate glasses with fixed NiO content (2 mol%) by substituting SiO 2 for B 2 O 3 , providing new insight into the role of mixed network formers in tuning optical, nonlinear optical, and gamma-ray shielding properties. The glass samples were synthesized via the conventional melt-quenching method. Optical absorption spectra exhibited characteristic ligand-field transitions of Ni 2+ ions. Also, there is a noticeable blue shift of the absorption edge with increasing SiO 2 content. Consequently, the optical band gap increased from 3.28 to 3.44 eV, reflecting enhanced network polymerization and stronger Si–O bonding. Moreover, the nonlinear optical parameters, including nonlinear refractive index and third-order nonlinear susceptibility, decreased with SiO 2 enrichment, which is attributed to reduced electronic polarizability arising from increased network rigidity. Furthermore, radiation shielding parameters—including mass and linear attenuation coefficients, half-value layer, mean free path, and effective atomic number—showed systematic composition-dependent variation. Notably, improved attenuation efficiency with increasing SiO 2 content is correlated with increased density and modified structural packing of the glass network. Among the investigated compositions, the SiO 2 -rich sample (NaBNiSi-40) exhibited superior shielding efficiency and a lower half-value layer compared to conventional shielding materials. These findings demonstrate that controlled manipulation of mixed glass formers offers an effective strategy for designing multifunctional materials with optimized optical and radiation shielding performance.