Regulating Oxygen Vacancies to Enhance Dipole and Interface Polarization for Highly Efficient Electromagnetic Wave Absorption in SiC@MnO ₂ Nanocomposites

Abstract At present, atomic‐scale defect engineering has become a primary strategy for precisely regulating the inherent properties associated with the electronic structure of semiconductors. However, concurrent phenomena and factors during the introduction of defects constrain researchers’ understanding of the correlation between desired defects in various transition metal oxides, electromagnetic parameters, and electromagnetic wave absorption. In this study, MnO ₂ nanoneedle arrays are pre‐prepared on the surface of SiC nanowire‐based carriers via a hydrothermal method, subsequently, oxygen vacancy is successfully introduced into the as‐fabricated sample by a simple calcination process. By precisely adjusting the heat‐treatment temperature, the oxygen vacancy accumulation‐induced in situ phase transformation from MnO ₂ to Mn ₃ O ₄ , creating intrinsic heterointerfaces. Under the synergistic effects of vacancy‐induced dipole polarization and interfacial polarization of derived MnO ₂ @Mn ₃ O ₄ heterogenerous interface, the optimal sample exhibits a minimum reflection loss (RL _min ) of −47.96 dB at a matching thickness of 1.90 mm, along with a favorable effective absorption bandwidth (EAB) of 6.40 GHz covering the entire Ku band at a matching thickness of 2.02 mm. This work pionners a defect‐driven phase transition strategy to elucidate the relationship between oxygen vacancy concentration, heterostructure interface properties, and EMW absorption capabilities, paving the way for practical application of defect engineering in EMW absorption.