Ti³⁺self-doped dark TiO₂nanoparticles with tunable and unique dielectric properties for electromagnetic applications

Robust, conductive and stable Ti³⁺self-doped dark TiO₂nanoparticles (Ti₄O₇) called Magnéli phases are attractive in electromagnetic (EM) applications due to their tunable dielectric properties. Herein, Ti₄O₇ceramic nanoparticles were successfully synthesized through a solvothermal and annealing method. To the best of our knowledge, this is the first time the dielectric and microwave absorption properties of Ti₄O₇nanoparticles have been investigated in the field of EM applications, and Ti₄O₇was evenly dispersed into polyimide (PI) by a heat pressing process. Interestingly, due to the formation of Ti³⁺and oxygen vacancies during the annealing process, the special crystal structure will form electron channels that promote dark TN nanoparticles to possess a higher electrical conductivity and show outstanding dielectric loss compared to pristine TiO₂powders, endowing the 60 wt% Ti₄O₇/PI hybrid with an exceptional RL reaching −49.3 dB of 13.7 GHz at 1.25 mm thickness. These consequences indicate that highly conductive dark Ti₄O₇composites will be good candidates for designing absorbers and other EM applications.