Tailoring optical nonlinearity and gamma-ray shielding in $$\:{\mathbf{B}\mathbf{i}}_{2}{\mathbf{O}}_{3}$$ -modified borate–BCZT glasses

This study investigates the structural, optical, nonlinear, and gamma-ray shielding properties of $$\:{\text{B}\text{i}}_{2}{\text{O}}_{3}$$ – $$\:{\text{B}}_{2}{\text{O}}_{3}$$ –BCZT glasses with composition x $$\:{\text{B}\text{i}}_{2}{\text{O}}_{3}$$ + (30–x) $$\:{\text{B}}_{2}{\text{O}}_{3}$$ + 70[( $$\:{\text{B}\text{a}}_{0.85}{\text{C}\text{a}}_{0.15}$$ )( $$\:{\text{T}\text{i}}_{0.9}{\text{Z}\text{r}}_{0.1}$$ ) $$\:{\text{O}}_{3}$$ ] (x = 0–25 mol%) synthesized via the conventional melt-quenching technique. X-ray diffraction (XRD) confirmed the amorphous nature of all samples, while density increased from 3.622 to 5.788 g/cm³ (~ 60% enhancement) with increasing $$\:{\text{B}\text{i}}_{2}{\text{O}}_{3}$$ content, accompanied by an increase in molar volume, indicating significant modification of the glass network. Fourier transform infrared (FTIR) analysis revealed enhanced Bi–O bond formation and an increase in non-bridging oxygen (NBO), confirming network depolymerization. Optical absorption analysis showed a decrease in the optical band gap from 3.615 to 2.839 eV, accompanied by an increase in Urbach energy, indicating enhanced structural disorder and the formation of localized states. The nonlinear optical parameters exhibited significant enhancement due to the high polarizability of Bi³⁺ ions. In addition, radiation shielding performance, evaluated using Phy-X/PSD in the energy range 15 keV–15 MeV, showed improved mass attenuation coefficient and effective atomic number, and a reduced half-value layer with increasing $$\:{\text{B}\text{i}}_{2}{\text{O}}_{3}$$ content. This work presents a systematic, concept-driven approach to tailoring borate–BCZT glasses via controlled $$\:{\text{B}\text{i}}_{2}{\text{O}}_{3}$$ incorporation, enabling stable glass formation even at low $$\:{\text{B}}_{2}{\text{O}}_{3}$$ former content (down to 5 mol%). More importantly, the study establishes a quantitative structure–property–function relationship linking $$\:{\text{B}\text{i}}_{2}{\text{O}}_{3}$$ -induced structural modifications with the simultaneous enhancement of the nonlinear optical response and gamma-ray shielding performance. Unlike previous studies that treat these properties separately, the present work demonstrates their integrated optimization within a single system, highlighting the potential of these glasses for advanced photonic and radiation protection applications.