Epoxy Composites Filled With Hydrothermally Synthesized ( BiO ) ₄ CO ₃ ( OH ) ₂ @ Gd ₂ O ( CO ₃ ) ₂ · H ₂ O Exhibiting Enhanced Gamma Ray Shielding Performance and Thermal Stability

ABSTRACT The development of efficient gamma‐ray shielding materials is crucial for addressing increasingly complex radiation environments. In this study, (BiO) ₄ CO ₃ (OH) ₂ (BCH) and (BiO) ₄ CO ₃ (OH) ₂ @Gd ₂ O(CO ₃ ) ₂ ·H ₂ O (BG) fillers were synthesized via a hydrothermal method. After being dispersed into epoxy resin by mechanical stirring, the mixtures were molded using a vacuum‐assisted thermal curing process. Under 59.5 keV gamma irradiation, the linear attenuation coefficient (LAC) of BG/EP‐50 reached 5.8 cm ⁻¹ , representing an 84% increase compared to BCH/EP‐50 (3.15 cm ⁻¹ ) and about 33 times that of pure EP (0.17 cm ⁻¹ ). In addition, the temperature at 50% weight loss (T _50% ) of BG/EP‐50 increased to 637.9〬C, which is 60.9% higher than that of the epoxy matrix, indicating improved thermal stability. The BG filler, constructed through a simple two‐step hydrothermal route, demonstrated a synergistic effect between Bi and Gd components, which not only compensated for the limitations of Bi in the low‐energy region but also enhanced the gamma shielding capability of the epoxy resin at higher energies. Compared to several shielding materials reported in recent years, BG/EP‐50 shows superior performance and offers a promising strategy for lightweight and environmentally friendly polymer‐based gamma shielding materials.