Microstructure, magnetic and low-frequency microwave absorption properties of doped Co–Ti hexagonal barium ferrite nanoparticles

In this work, the Co²⁺-Ti⁴⁺ co-doped hexagonal barium ferrite Ba(CoTi)_xFe_12-2xO₁₉ (x = 1.0, 1.2, 1.4, abbreviated as BFCTO-x) nanoparticles were synthesized by sol-gel method. The XRD and SEM confirm that the BFCTO-x nanoparticles are of high quality of single hexagonal system with sheet nanostructure and average grain size about 200 nm. With the increase in x from 1.0 to 1.4, the magnetic properties H_c and M_r of nanoparticles decreased rapidly suggest that Co²⁺-Ti⁴⁺ co-doped induced more vacancy defects. Relying on the synergistic effects from dielectric loss and magnetic loss, as well as the abundant interface and ion substitution defects of nanoscale particles, the samples show an excellent microwave absorption performance at the lower frequency (<10 GHz). The minimum reflection loss (RL_min) of BFCTO-1.4 can reach −52.36 dB at 8.44 GHz with thickness of 4.64 mm, and a broad 6.97 GHz bandwidth over −10 dB, while the BFCTO-1.2 could reach −49.73 dB at 2.92 GHz. Based on the superior performance in both absorbing intensity and effective bandwidth, Ba(CoTi)_xFe_12-2xO₁₉ nanoparticles can be a promising candidate in application to low-frequency microwave absorption.