Ultra‐Thin Oxide‐Based Double‐Layer Architecture Achieves Wide‐Temperature Broadband Microwave Absorption by Synergizing Lorentz Resonance and Thermionic Transport

Abstract Achieving high and stable permittivity is essential for developing ultra‐thin and wide‐temperature adaptive microwave‐absorbing materials (MAMs). Conventional high‐permittivity MAMs suffer from temperature‐sensitive permittivity and cannot achieve stable microwave‐absorbing performance at fluctuating temperatures, while temperature‐insensitive MAMs exhibit low permittivity that severely restricts ultra‐thin designs. Herein, a double‐layer La ₂ Zr ₂ O ₇ /Eu ₂ Zr ₂ O ₇ architecture is employed, with rare‐earth zirconates featuring with one‐eighth anion‐site vacancies, as a promising candidate for ultra‐thin wide‐temperature adaptive MAMs. The established balance between thermionic relaxation polarization and Lorentz dielectric resonance—activated by oxygen ions—can largely increase the real part of permittivity of La ₂ Zr ₂ O ₇ while maintaining its stability at different temperatures. Concurrently, strong thermionic transport induces an increase in dielectric loss capacity of Eu ₂ Zr ₂ O ₇ , which can broaden effective absorption bandwidth (EAB) effectively. Moreover, the macroscopic interfacial resonance between two layers overcomes the limitations imposed by the quarter‐wavelength theory, generating new absorption peak for further expanding EAB. Under synergistic coupling of these mechanisms, it is successfully achieved superior EAB—completely covering the Ku band (12.4–18 GHz) over a wide‐temperature range (400–800 °C) at an ultra‐thin fixed thickness of just 1.2 mm, coupled with a maximum EAB/ d of 3.6 GHz mm ⁻¹ . This innovative design offers promising pathways for developing ultra‐thin and wide‐temperature adaptive MAMs.