Multi-heterointerface lightweight ceramics achieving temperature-insensitive dielectric properties for high-temperature electromagnetic wave effective absorption

The limitations of conventional electromagnetic wave (EMW)-absorbing materials in terms of high-temperature resistance have stimulated interest in the development of high-temperature EMW-absorbing materials across various fields. However, owing to the temperature dependence of the permittivity, achieving effective EMW absorption across a wide temperature range remains a significant challenge for high-temperature EMW absorbing materials. Herein, a novel molecular-scale strategy is proposed for the in situ construction of multiple heterointerfaces during the polymer-derived ceramic (PDC) process, thereby achieving temperature-insensitive permittivity. The interfacial dipole polarization generated by multiple heterointerfaces effectively mitigates the dependence of the permittivity on conductivity, thereby reducing the temperature sensitivity of the overall permittivity. Moreover, the preparation of lightweight porous ceramics was further achieved via the self-sacrificing template method. As a proof-of-concept, multiheterointerface lightweight ceramics (MHLCs) that exhibit excellent thermal stability (up to 1000 °C), low density (1.03 g/cm³), low thermal conductivity (0.37 W/(m·K)), and high bending strength (33.55 MPa) have been designed and fabricated. These ceramics demonstrate excellent temperature-insensitive EMW absorption performance and thickness robustness, effectively absorbing X-band EMW across a temperature range from 25 to 900 °C at various thicknesses. This approach to developing temperature-insensitive dielectric ceramics significantly improves the performance and functionality of high-temperature EMW absorbing materials, thereby providing substantial guidance and reference value.