Enhancing Optical and Radiation Shielding Characteristics in La ₂ O ₃ -Doped Bi ₂ O ₃ –BaO–PbO ₂ –B ₂ O ₃ Glasses

Heavy metal oxide glasses are currently being investigated as potential alternatives to these traditional materials due to their high density and tunable properties. However, there is limited information regarding the combined effects of lead oxide (PbO2) and lanthanum oxide (La2O3) on the properties of borate glasses. The purpose of the current study will be to examine the effect of adding La2O3 to the borate glass system on the structural, optical, and gamma-ray shielding properties. The Bi2O3–BaO–PbO2–B2O3–La2O3 glass system was prepared according to a standard melt–quench methodology, to explore La2O3 concentration’s impact on its optical properties and γ-ray shielding ability. UV-visible spectroscopy confirmed the amorphous nature of the glasses, with the absorption edge shifting toward longer wavelengths with increasing La2O3 content. The optical band gap decreased from 2.976 to 2.839 eV (direct) and from 2.823 to 2.622 eV (indirect), while the refractive index increased from 2.404 to 2.507, indicating enhanced polarizability and structural modifications in the glass network. The Urbach energy (E) decreased from 0.282 to 0.254 eV, suggesting a reduction in localized defect states and improved structural ordering at higher La2O3 concentrations. FTIR analysis suggests the coexistence of BO3 and BO4 structural units, with indications of both non-bridging oxygen formation and partial structural reorganization. These results indicate that La2O3 incorporation leads to a balance between network depolymerization and structural stabilization, which governs the observed optical properties of the glasses. The gamma radiation shielding characteristics, computed from the Phy-X/PSD software in the energy range of 0.015 to 15 MeV, indicated that the 26Pb3La glass (0.3 wt% La)–based material had the greatest attenuation capability, with mass attenuation coefficient and linear attenuation coefficient of 64.523 cm2/g and 326.679 cm−1 at 0.015 MeV, respectively. The half-value layer ranged from 0.0021 to 6.17 cm as the energy increased, and the effective atomic number (Zeff) ranged from 70.19 to 73.75. The incorporation of La2O3 and PbO2 raises the glasses’ radiation shielding efficacy, as the effective atomic number values evidence, which exhibit the sequence 17Pb0La < 20Pb1La < 23Pb2La < 26Pb3La. When evaluated with commercial glass and barite concrete, the 26Pb3La sample had enhanced shielding performance compared to the other investigated compositions, making it an attractive radiation-shielding material for medical and nuclear applications.