YCoO₃ has unique advantages in functional applications owing to its exceptional lattice stability, valence adaptability, and environmental resistance; however, its potential for microwave absorption remains largely unexplored. In this study, Y_0.9Sr_0.1Co_1−xFe_xO₃ (x = 0–0.2) perovskite absorbers were synthesized via a sol–gel method, which demonstrated superior microwave absorption performance. Oxygen vacancy engineering facilitates Co redox cycling, significantly enhancing oxygen ion mobility and conductivity loss. First-principles calculations revealed that Fe³⁺doping not only intensifies crystal polarization but also improves magnetic properties, thereby synergistically optimizing dipole polarization and magnetic losses. Additionally, the nanoscale particle morphology enhances the interfacial polarization effects. The optimal composition (x = 0.1) achieves an effective absorption bandwidth (EAB) of 5.71 GHz with a reflection loss (RL) of −47.18 dB at a thickness below 1.8 mm, demonstrating a significant enhancement over that of the undoped material. This work provides new insights into the design of ultrathin, high-performance absorbers while elucidating the fundamental loss mechanisms in perovskite-based systems.

Alkali and Co²⁺ co-modulation has seldom been investigated as a prospective strategy to achieve high-efficient microwave absorbing (MA) materials. In this work, a new alkali and Co ion exchange co-modulation strategy was first reported, leading to broadband MA capacity through simultaneous manipulating multiple factors, such as composition, micromorphology, and heterogeneous interface. And enhancements in impedance matching and magnetic–dielectric loss were synergistically realized. Consequently, the optimized FeCo alloy@porous carbon (FPC) nanocomposite with the alkali regulation delivered an effective absorption bandwidth (EAB) of 6.72 GHz, making it the merely single FeCo-based metal-organic framework derived FPC absorber with a low filler content of 15 wt.%. Interestingly, the nanocomposites by ion exchange strategy realized the switchable “on/off” states on electromagnetic response. Furthermore, the radar cross-section (RCS) reduction value of the products reached 25.6 dB·m² under the incident angle of 0°. In brief, this work not only offers the special role of alkali and Co²⁺ co-modulation in composition regulation, structure design, and MA capacity, but also provides a reliable strategy to develop smart nano-absorbers to cope with electromagnetic pollution issues.