Nitrogen-doped rutile TiO₂ enhances microwave absorption performance by constructing defect dipoles

Advanced microwave absorption materials have significant application value in electromagnetic pollution protection and military stealth technology. Traditional rutile TiO₂ has limited loss capacity in the microwave frequency range and is used as an impedance matching component. In this study, a nitrogen (N)-doped TiO₂ material with controllable point defects was successfully prepared through a sol-gel method. Experimental results show that the N doping strategy can effectively regulate the complex dielectric constant and microwave absorption performance of the materials. When the N/Ti molar ratio is 1.7, at a 2.0 mm matching thickness, a minimum reflection loss (RL_min) of -37.5 dB was obtained, and an effective absorption bandwidth (EAB, RL < -10 dB) of 3.4 GHz was achieved. Through characterization methods including electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), it was confirmed that the regulating concentration of oxygen vacancies induced by N doping and the composite defects as strong polarization centers significantly enhanced the defect dipole polarization. This study not only provides a new approach for optimizing the intrinsic microwave absorption performance of rutile TiO₂ at the lattice level through point defect engineering but also expands the application potential in the microwave absorption field.