Synergistic Electron Density and Oxygen Defect Regulation in Fluorite High-Entropy Oxides for Superior Ionizing Radiation Shielding

Lightweight and lead-free radiation shielding materials remain urgently needed. This work designed a fluorite high-entropy oxide (FHEO) system through a combined computational–experimental route. Density functional theory based on special quasi-random structures was used to identify thermodynamically stable fluorites from a wide compositional space. Their γ-ray attenuation potential in polypropylene (PP) composites was then evaluated, and the best candidates were selected for ultrafast Joule-heating synthesis. Guided by this workflow, LaSm-1000/PP composite showed broad-spectrum shielding performance and surpassed PbO/PP at identical loadings. Its linear attenuation coefficients were 5.67, 0.48, 0.38, and 0.34 cm⁻¹ at 59.5, 662, 1173, and 1332 keV, respectively. X-ray photoelectron spectroscopy and projected density of states revealed an electron density–oxygen defect synergy in optimized FHEO. Lattice distortion and uniform cation distribution suppressed oxygen defects, stabilized Bi³⁺ and W⁶⁺, and broadened O 2p states. These electronic features enhanced photoelectric absorption at low energies and promoted Compton scattering at medium and high energies. The proposed design route provides an efficient and scalable strategy for next-generation lead-free radiation shielding materials.