Rare‐Earth–Sulfur Surface Modification Enables SiC Ceramics for Low‐Frequency Electromagnetic Wave Absorption in Extreme Environments

The development of low‐frequency electromagnetic wave (EMW) absorbers with excellent stability in extreme environments remains a major challenge for radar stealth and anti‐electromagnetic interference applications. Herein, a rare‐earth–sulfur (RE─S) (RE = La, Ce, Pr, Sm, Gd, Er) surface modification strategy is first proposed to regulate the electromagnetic response of SiC‐based ceramics via surface chemical bond evolution from Si─O to RE─O species. This process transforms fast‐relaxation dipoles into slow‐relaxation dipoles, thereby prolonging the polarization relaxation time and inducing a low‐frequency shift in the absorption peak from the Ku band to the C band. The optimized SiC/Ce–S ceramics exhibits a minimum reflection loss ( R L ) of −60.08 dB at 5.76 GHz, while the strategy demonstrates broad universality across multiple RE elements. The enhanced EMW absorption performance is attributed to the synergistic regulation of surface chemistry, dipole polarization, and dielectric relaxation. Moreover, the RE─S modified ceramics show rapid thermal response, excellent corrosion resistance, and outstanding oxidation stability, retaining an R L of −54.46 dB at 5.44 GHz after annealing at 500°C. This work provides a viable strategy for designing multifunctional SiC‐based EMW absorbers for operation in extreme environments.