Impact of substituting Al2O3 with CuO on the structural, optical, thermal, mechanical, and gamma-ray attenuation properties of B2O3–Bi2O3–K2O–Al2O3 glass system

Aluminium potassium bismuth borate (ACKB) glasses with the composition 63.8B2O3–15Bi2O3–20K2O-(1.2-y)Al2O3-yCuO (where y = 0.0, 0.3, 0.6, 0.9, and 1.2 mol%) were synthesized via the melt-quenching method to study the impact of substituting Al2O3 with CuO on their structural, optical, thermal, mechanical, and gamma-ray attenuation properties. X-ray diffraction confirmed their amorphous nature, while Fourier transform infrared spectroscopy identified structural units present in the glass matrix. Substituting Al2O3 with CuO increased glass density and reduced molar volume due to a decrease in boron-boron distance. Structural analysis revealed a transition from BO3 to BO4 units at 0.3 mol% CuO, associated with the formation of distorted CuO6 units. At 0.6 mol% CuO, there was a slight increase in B–O–B linkages and CuO4 units, but higher CuO concentrations led to a reduction in B–O–B linkages. The optical band gap decreased at 0.3 mol% CuO, followed by a slight increase at 0.6 mol%, and then declined further due to depolymerization. Differential scanning calorimetry indicated a decrease in glass transition temperature with increasing CuO content, attributed to a reduction in B–O–B linkages. Mechanical properties, modeled using the Makishima-Mackenzie theory, showed improvements in microhardness and elastic moduli with the substitution of Al2O3 by CuO. Gamma-ray attenuation, evaluated using Phy-X/PSD and XCOM software, increased with higher CuO content. Among the investigated compositions, the glass sample with 0.6 mol% CuO demonstrated slightly lower gamma-ray attenuation than the 1.2 mol% CuO sample. However, its remarkable thermal stability, reflected by a higher glass transition temperature (328.845 °C compared to 324.092 °C), makes it a highly promising candidate for gamma-ray shielding applications, particularly at 0.662 MeV, where a balance between thermal stability and mechanical strength is critical.