Assessing gamma-ray shielding effectiveness in alloy europium-modified Zintl-phase

The gamma-ray shielding performance of a quaternary Zintl-phase alloy system with the composition Ca 9−γ Eu γ Zn 4.7 Sb 9 (y = 0, 1.125, 3.375, and 5.0 mol%), designated CEZS1–CEZS4, was investigated across the photon energy range of 0.015–15 MeV. The mass attenuation coefficients were calculated using Geant4 simulations and Phy-X/PSD software, yielding mutual agreement with relative deviations below 1%. The results showed that CEZS4 composition achieved the highest shielding performance among the investigated series, with a mass attenuation coefficient of 0.0977 cm 2 /g at 0.511 MeV and 0.0795 cm 2 /g at 0.662 MeV, and a linear attenuation coefficient enhancement of 27–65% relative to the Eu-free reference (CEZS1) across the full energy range. This enhancement translated into 22–40% reductions in the half-value layer, tenth-value layer, and transmitted photon intensity. Distinct absorption-edge features corresponding to the K-edges of antimony and europium were resolved in the effective-atomic-number and radiation-protection-efficiency profiles. The effective atomic number increased from ~ 35 to ~ 54 within the K-edge activation window, while the tenth-value-layer maximum in the pair-production range shifted from 17 cm (CEZS1) to 12.5 cm (CEZS4). The radiation protection efficiency declined beyond 50 keV, with Eu enrichment providing an improvement of approximately 25% points at 100 keV. Comparative evaluation at 0.662 MeV indicated that the CEZS4 composition provides higher linear attenuation than most reported polymer-composite, ceramic, and glass shielding materials, and performs within the range of several established metallic alloys. The obtained results indicate that the CEZS4 composition can be considered for use in compact medical shielding components, portable diagnostic equipment, and industrial gamma source enclosures where reduced shielding thickness is required.