Broadband electromagnetic absorption up to 1473 K enabled by dielectric frequency-dispersion engineering in ceramic composites

Rising vehicle Mach numbers urgently necessitate broadband electromagnetic wave (EMW) absorbers capable of operating at even higher temperatures while maintaining environmental durability. However, Current high-temperature EMW absorbing materials face the restriction and temperature-sensitivity of dielectric frequency-dispersion (FD), which often forces reliance on complex macro-structures to broaden effective absorption bandwidth (EAB). Here, inspired by the concept of finite element method, we propose a controlled FD regulation strategy to overcome this by employing multivariate ultra-high temperature ceramic (UHTC) borides with tunable surface oxide thickness. The fabricated material (without structural design) yields a broad EAB of 26.98 GHz at just 2.8 mm thickness, alongside environmental resistance. Crucially, the multivariate polarization remains effective for FD regulation even at 1473 K, enabling our material to harvest an EAB of 10.26 GHz after applying an oxide layer, showing bright application prospects for the stealth of high-speed vehicles. This work proposes multivariate frequency-dispersion regulation approximation under the protection of an oxide layer to overcome the challenge of HT broadband EM wave absorption of monomer ceramics, allowing wide-band absorption from RT up to 1473 K.