High-temperature oxide ceramic microwave absorber enabled by thermionic migration mediated by electron delocalization.

The escalating demand for long-term high-temperature microwave-absorbing materials (HTMAMs) in high-speed aerospace stealth is hindered by limitations such as magnetic loss degradation or oxidation risks. Herein, we introduce rare earth zirconate ceramics that exhibit air stability up to 1600 °C. Abundant oxygen vacancies significantly enhance permittivity and thus microwave-absorbing performance through activated thermionic migration at elevated temperatures. Moreover, the thermionic-facilitated permittivity can be meticulously modulated by electron delocalization, with the extent governed by lattice disorder. We demonstrate this concept through a dual-layer Er₂Zr₂O₇/Gd₂Zr₂O₇ structure to further optimize impedance matching, achieving an ultra-wide bandwidth (8.27 GHz) and strong absorption (-64.61 dB) at ultrathin thicknesses under 1.2 mm at 600 °C mainly by macroscopic interfacial resonance, alongside an ultralow thermal conductivity (1.61 W•m^-1•K^-1). This work presents an innovative approach to design high-performance and anti-oxidative HTMAMs through thermionic migration tuned by electron delocalization, advancing structural-functional integrated materials for extreme environments.