Melt-Quenched Zinc Sodium Borate Glasses: Understanding the Role of ZnO/Na2O Ratio in Density, Band Gap, and Radiation Attenuation

In this work, we successfully prepared glasses with the composition 55 B2O3 – (45-x) ZnO – x Na2O (x = 0, 5, 10, 15) using the traditional melt quenching procedure. We analyzed the influence of substituting ZnO with Na2O at different concentrations on the attenuation of ionizing radiation and the glass density. Different analytical tools, such as XRD, FTIR, and UV-VIS spectroscopy, were used to investigate the crystal structure and optical features of the produced samples. The partial replacement of ZnO by Na2O significantly reduces the density (from 3.36 to 2.87 g/cm3) and, in contrast, increases the molar volume of the glass (from 22.32 to 25.06 cm3/mol.). The positions of the main peaks in the FTIR spectra remain relatively unchanged with increasing Na₂O content. The Fermi energy (EF) of the glasses increases from 3.16 to 3.45 eV with increasing Na2O concentration. Samples with higher Na2O exhibit a blue shift in the UV cutoff. The direct and indirect optical band gap energy values (Ed/Ein) increase from 3.42 to 3.62 eV and 2.87 to 3.23 eV, respectively, with increasing Na2O concentration. The radiation attenuation performance of these glass samples was examined through evaluation of various parameters like linear and mass attenuation coefficients (LAC/MAC), effective atomic number (Zeff), and half-value layer (HVL) and tenth-value layer (TVL) in the photon energy range of 10 keV–15 MeV. LAC and MAC values decrease with decreasing ZnO content. The two buildup factors, energy (EBF), and energy absorption (EABF) have been recorded for the different compositions at penetration depths up to 40 mean free paths. Samples with the highest ZnO concentration show the lowest HVL and TVL values at the lowest photon energy (≤ 2 MeV). Increasing Na2O concentration significantly increases both EBF and EABF, with their maxima occurring at 5 MeV. Increasing zinc oxide in the glass improves its radiation shielding ability, suggesting potential applications for zinc alkali borate glasses in radiation protection.