Ti3+ self-doped dark TiO2 nanoparticles with tunable and unique dielectric properties for electromagnetic applications

Abstract

Robust, conductive and stable Ti³⁺ self-doped dark TiO₂ nanoparticles (Ti₄O₇) called Magnéli phases are attractive in electromagnetic (EM) applications due to their tunable dielectric properties. Herein, Ti₄O₇ ceramic 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 Ti₄O₇ nanoparticles have been investigated in the field of EM applications, and Ti₄O₇ was 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 TiO₂ powders, 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 Ti₄O₇ composites will be good candidates for designing absorbers and other EM applications.