Effect of AB-site co-doping on the electromagnetic wave absorption properties and mechanism of LaCoO3 perovskite oxides

La 1- x Sr x Co 0.9 Fe 0.1 O 3 ( x  = 0, 0.1, 0.15, 0.2) perovskite oxides were successfully synthesized by the sol–gel method, with Sr 2 ⁺ doping at the A-site and Fe 3+ at B-site of LaCoO 3 . The effect of AB-site co-doping on the structure, morphology, electromagnetic parameters, and microwave absorption properties was systematically investigated. The optimal composition La 0.85 Sr 0.15 Co 0.9 Fe 0.1 O 3 achieved a minimum reflection loss of −42.79 dB at 1.5 mm thickness and an effective absorption bandwidth of 5.44 GHz (11.92–17.36 GHz) at 1.8 mm. This remarkable performance arises not only from the presence of defects and the enhanced polarization loss due to oxygen vacancies induced by Sr 2+ and Fe 3+ co-doping, but also from synergistic effects including multiple reflections and scattering from the porous microstructure, interfacial polarization, and magnetic loss mechanisms. These results demonstrate that simultaneous A-site and B-site doping is an effective strategy to achieve thin, broadband, and high-performance microwave absorbers, highlighting a promising route for the development of perovskite-based EM wave absorption materials.