Improved electromagnetic microwave absorption of the annealed pre-sintered precursor of Mn-Zn ferrite

The pre-sintered precursor of the Mn-Zn ferrites was used as starting materials to make a material with good electromagnetic microwave absorption. X-ray photoelectron spectra (XPS) analyses show that more Mn2+ and Zn2+ moved to the surface of particles to form non-stoichiometric (Mn, Zn)Fe2O4 ferrite under annealing with a partial H2, improving the electromagnetic impedance matching. Regarding the original precursor, the lowest reflection loss is about −2.9 dB at 6.3 GHz for a 5 mm thick absorber. After vacuum annealing, the lowest reflection loss is around −34.8 dB at 5.9 GHz for 4 mm thick absorber. The lowest reflection loss of −47.6 dB was obtained at 13.2 GHz with a 1.85 mm thick absorber after annealing under a partial H2. This work proposes a simple way to make a good electromagnetic microwave absorption material starting from the pre-sintered precursor of Mn-Zn ferrites.