Synergistic magnetic-dielectric effect of LiNb_0.8Ti_0.25O₃@carbonyl iron powders resin-based coatings for efficient electromagnetic wave absorption

Commercially thin microwave absorbing materials (MAM) often rely on a high proportion of magnetic metal powder as absorbents, leading to excessive loss, impedance mismatch, and high density. LiNb_0.8Ti_0.25O₃, which has attracted attention in the fields of microwave devices and microwave communications due to its high microwave dielectric constant and low loss characteristics, was therefore incorporated as a high-permittivity phase with traditional microwave absorbers to effectively tailor the complex permittivity of the composites. In this study, LiNb_0.8Ti_0.25O₃ and carbonyl iron powders were composited, and resin-based MAM coatings were prepared via air spraying. The performance of the coating was investigated under the premise of significantly reducing density. Electromagnetic parameters, hysteresis loops, and electromagnetic simulations were employed to comprehensively analyze the electromagnetic response mechanisms and absorption performance of the materials. The combination of dielectric powders and magnetic powders enabled tunable magnetic loss and narrowband dielectric resonance while exhibiting specific dielectric dispersion. This approach facilitated the optimization of impedance matching, achieving absorption peaks at specific thicknesses and frequencies (e.g., RL_min of −53.51 dB at 4.28 GHz with a thickness of 2.9 mm). Additionally, the synergy between dielectric and magnetic responses resulted in an enhanced effective absorption bandwidth, reaching 5.77 GHz (12.23–18 GHz) at 1.2 mm and covering the entire Ku-band. This study provides valuable insights for researchers aiming to achieve further breakthroughs in absorption performance through the incorporation of functional composites based on metallic powders and other strong electromagnetic response powders.