Tunable magnetic and microwave absorption properties of barium ferrite particles by site-selective Co2+-Zr4+Co-doping

Co2+-Zr4+ ion-doped barium ferrite (BaFe12-2x(CoZr)xO19, x = 0.3, 0.4, 0.5) particles were prepared by a citrate sol-gel method. It is found that a single M-type barium ferrite phase exists in particles fabricated with a relatively high ion doping amount, which indicates Co2+ ions can balance the system valence and aid the entry of high-valent Zr4+ ions. With the increase in doping amount, the lattice constant and the particle size gradually increase. Moreover, the content of Fe2+ is at a lower level, and the oxygen vacancy con-centration first increases and then plateaus. According to the results of first-principles calculation and Mossbauer spectral analysis, doping ions tend to replace Fe3+ at 4 f2, 4 f1, and 2b sites, continuously de-creasing the coercivity and saturation magnetization. Multi-doping effectively introduces dual magnetic resonances and multiple polarization, and reduces the natural resonance frequency. In addition, it improves the impedance matching performance and the electromagnetic attenuation capabilities, leading to an ex-cellent absorption performance in the Ku-band. The co-doped barium ferrites produce obvious interference cancellation at a specific thickness, further improving the absorption ability. The BaFe11Co0.5Zr0.5O19 can achieve the maximum microwave absorption bandwidth of 6.08 GHz, covering the entire Ku-band. When the matching thickness is 2.05 mm, it also exhibits the minimum reflection loss of - 48.16 dB at 11.94 GHz. The above results suggest that this co-doped barium ferrite possesses great potential in microwave ab-sorption applications.& COPY; 2023 Elsevier B.V. All rights reserved.