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.

Titanium dioxide (TiO₂) exhibits weak surface electron polarization and a poor response in the microwave region, resulting in its limited electromagnetic (EM) loss capability, which restricts its application in EM wave absorption. Recent research has revealed that the reduced phase of TiO₂, denoted as Ti_xO_2x-1 (1≤x≤10), possesses both metallic and semiconducting properties. This duality, coupled with its relatively high electrical conductivity, positions Ti_xO_2x-1 as a promising candidate for the next generation of EM wave absorbers. However, current investigations into Ti_xO_2x-1 absorbers primarily focus on the EM property modulation of black TiO₂ and its composites, while the influence of crystal structure, lattice defects, and band structure on the EM parameters and absorption performance of Ti_xO_2x-1 absorbers remains unclear. Consequently, there is a lack of a comprehensive Ti_xO_2x-1 absorber system both domestically and internationally. Based on the fundamental principles of EM wave absorption materials, this study discusses the crystal structure and formation mechanism of Ti_xO_2x-1 and defective TiO₂, as required by semiconductor metal oxides. The paper summarizes the high-efficiency EM wave absorption properties of TiO₂-derived Ti_xO_2x-1 absorbers with various texture designs, achieved through defect engineering and interface engineering. Focusing on the challenges of "poor absorbing performance" and "unclear absorbing mechanisms" in Ti_xO_2x-1 absorbers, this work aims to achieve optimal design of Ti_xO_2x-1 materials, enhance their absorbing capabilities, and establish an electromagnetic control mechanism for oxide-semiconductor absorbers. By employing methods such as defect regulation, compositional optimization, and interface design, multiple EM loss mechanisms including conductivity loss, dipole polarization, interface polarization, and coupling effects, are established and optimized. Accordingly, this approach improves the impedance matching and EM loss capabilities of Ti_xO_2x-1-based absorbers, ultimately resulting in absorbers with superior wave-absorbing performance. Finally, by integrating domestic and international research progress, this paper proposes a novel design strategy for Ti_xO_2x-1 absorbers, which holds significant implications for the future development and application of semiconductor metal oxide absorbers.