Valence–Vacancy Coupled Loss Engineering in LaMnO₃ Perovskites for Low-Frequency Microwave Absorption

The high-efficiency absorption of low-frequency electromagnetic waves remains a key bottleneck in electromagnetic protection. Conventional carbon/magnetic fillers are limited by excessively large skin depth, limited magnetic response, and oxidation-induced parameter drift at elevated temperatures, making it difficult to simultaneously satisfy low-frequency absorption and high-temperature durability. This work proposes a charge imbalance–driven Jahn–Teller strategy and fabricates single-phase La_1–xCa_xMnO₃ perovskites via a sol–gel method. The Ca²⁺/La³⁺ ionic-size mismatch induces MnO₆ octahedral distortion and is accompanied by Mn³⁺/Mn⁴⁺ redistribution and oxygen-vacancy evolution, which strengthens polarization-related dielectric loss and enables coordinated improvement in attenuation capability and impedance matching. Consequently, the dominant dielectric relaxation/absorption response is shifted toward lower frequencies. The optimized sample achieves a minimum reflection loss of −40.46 dB at 4.72 GHz with an effective absorption bandwidth of 4.40 GHz. Far-field radar cross-section simulations further provide evidence of scattering suppression, with a maximum echo reduction of 30.7 dB·m² for a metal plate. This strategy is extendable to perovskite oxide systems and offers a generalizable design guideline for thermally robust low-frequency absorbing coatings.