Optimizing B2O3–Bi2O3–K2O glass via Al2O3 doping: Structural, thermal, optical absorption, elastic moduli, and γ-ray attenuation behavior

Utilizing the thermal fusion and rapid cooling technique, AKB glasses with the chemical formula (65-x)B₂O₃–15Bi₂O₃–20K₂O-xAl₂O₃ (0.0 ≤ x ≤ 1.2 mol%) were synthesized to systematically examine the role of Al₂O₃ in enhancing the structural, thermal, optical absorption, elastic moduli, and γ-ray attenuation behavior. The non-crystalline structure of the glasses was affirmed via XRD analysis. FTIR spectroscopy revealed that the incorporation of Al₂O₃ up to 0.6 mol% promotes the transformation of BO₃ units into BO₄ units, facilitating the development of additional non-bridging oxygen sites. However, beyond 0.6 mol% Al₂O₃, the formation of [AlO₄]^- units becomes more dominant compared to the highly distorted [AlO₆]^3- units. These [AlO₄]^- units interact with non-bridging oxygen atoms, facilitating charge stabilization and enhancing cross-linking within the glass network. A rise in density accompanied by a decline in molar volume, suggests a compaction of the glass network with increasing Al₂O₃ concentration. The optical band gap exhibited a decreasing trend up to 0.6 mol% Al₂O₃, indicating an increase in structural disorder. Nevertheless, for Al₂O₃ concentrations exceeding 0.6 mol%, the optical band gap increased, suggesting a transition toward a more ordered and cross-linked glass structure. DSC analysis further confirmed enhanced thermal stability, with the highest glass transition temperature of 337.556 °C occurring at 0.3 mol% Al₂O₃. The Makishima-Mackenzie model demonstrated an improvement in mechanical properties with Al₂O₃ doping, primarily due to the increase in mean bonding energy density. This enhancement strengthens the glass network, resulting in greater rigidity, superior mechanical stability, and improved overall structural integrity. γ-ray attenuation analysis revealed that the AKB glass samples exhibit superior attenuation efficiency compared to widely used commercial shielding materials, including RS-253-G1 and RS-360. While AKB glasses possess a half-value layer greater than 1.389 cm, exceeding that of RS-520, they still demonstrate superior shielding capabilities relative to concrete and other commercial glass alternatives. Among the AKB glass samples, the AKB0.3 (0.3 mol% Al₂O₃) composition exhibited outstanding thermal stability, as indicated by its higher glass transition temperature. This property makes it highly suitable for radiation shielding at 0.662 MeV, where thermal stability is essential for ensuring optimal performance.