Effect of Sm doping on structure and microwave absorption properties of brownmillerite oxide Ca2Fe2O5

Brownmillerite-type Sm x Ca 2- x Fe 2 O 5 ( x  = 0, 0.1, 0.2, 0.3, 0.4) was synthesized by sol-gel method. The results indicate that Sm doping effectively tailors the microstructure of the material and enhances both defect polarization and interface polarization, leading to improved dielectric properties. The pristine Ca 2 Fe 2 O 5 exhibited a maximum reflection loss (RL) of only −17.24 dB and an effective absorption bandwidth (EAB) of 2 GHz. In contrast, the doped Sm 0.2 Ca 1.8 Fe 2 O 5 exhibited the optimal EMW absorption performance: achieving an RL of −53.7 dB at a thickness of 1.8 mm, and an EAB of 5.04 GHz at 2.0 mm thickness, nearly covering the entire Ku band (12–18 GHz). This work provides valuable insights for the design and application of brownmillerite oxides in 5G shielding or radar stealth materials.