Geant4 simulation-based evaluation of gamma and neutron shielding properties of BaTiO₃/CaWO₄-reinforced polymer composites

The demand for lightweight, efficient, and eco-friendly radiation shielding has driven the development of advanced polymer composites. This study evaluates the gamma-ray and neutron attenuation properties of BaTiO₃- and CaWO₄-filled ternary polymer composites (5–20 wt%) using validated Geant4 Monte Carlo simulations (relative discrepancy ≤ 2% vs. experimental benchmarks). Key shielding metrics—linear and mass attenuation coefficients, half- and tenth-value layers, effective atomic number, effective electron density and energy buildup factors—were analyzed over 15 keV–1.5 MeV, complemented by neutron cross-section data at 4.5 MeV. Gamma attenuation improves monotonically with filler content. BaTiO₃ (20%) excels near 60 keV, while CaWO₄ (20%) performs optimally at the W K-edge (69.5 keV). In the photoelectric-dominated range (< 100 keV), CaWO₄ composites reduce HVL by 35–40% relative to BaTiO₃; differences shrink to < 15% in the Compton range (0.2–1 MeV) and vanish above 1 MeV, where HVL exceeds 8 cm for all samples. EBF decreases with higher filler loading, with CaWO₄ showing lower secondary radiation buildup than BaTiO₃. For fast neutrons (4.5 MeV), elastic scattering dominates (28–31%) due to the hydrogen-rich matrix. CaWO₄ (20%) exhibits the lowest transport fraction (69.11%) and shortest mean free path. However, neutron capture probabilities in oxide-doped composites remain negligible (< 0.0015%), highlighting the necessity of hybrid designs incorporating high-capture isotopes (e.g., Gd) for thermal neutron absorption. These results support an energy-specific material selection framework: CaWO₄ (20%) is preferred for low-energy gamma shielding (< 100 keV) and minimal secondary radiation, whereas BaTiO₃ (20%) offers competitive broadband performance. With low density and mechanical flexibility, these composites are suitable for medical radiology, nuclear facility linings, and aerospace applications.