Abstract
Recently, widespread microwave applications have generated plenty of unwanted electromagnetic radiation, which has become a global environmental pollution problem. Therefore, finding an efficient microwave absorbing material (MAM) is a trendy topic, and strontium hexaferrite (SrFe12O19, SrM) is a promising candidate. However, its high ferromagnetic resonance frequency (fFMR) prevents SrM from becoming an excellent MAM for wide-frequency range applications. Herein, as-prepared SrM samples with the morphologies of polygonal shape (Sr-P), rod (Sr-R), and porous ball-like (Sr-PH) were successfully prepared. Differences in morphology were effective to the static magnetic and optical properties. Furthermore, the fFMR of SrM was modified to the X-band frequency range. In particular, Sr-PH samples could reach reflection loss (RL) values of –10 dB for 2.5 and 3 mm thicknesses. The microwave absorption of SrM as-prepared samples could be enhanced by making the tri-layer microwave absorbers from as-prepared samples. The simulated RL curves of the 2mm tri-layer-absorber with Sr-PH as the top layer, Sr-R as the middle layer, and Sr-P as the bottom layer (Sr-PH/Sr-R/Sr-P) could achieve a minimum RL of –12 dB and an effective absorption bandwidth (EAB) value of 2.95 GHz. The microwave absorption performance was significantly increased with an increase of 0.5 mm in the total thickness of the tri-layer absorbers. In detail, the Sr-PH-0.5/Sr-R-1.5/Sr-P-0.5 absorber achieved the best values of RL and EAB at –20 dB (illustrating 99% of the microwave incident wave being absorbed) and 4 GHz (covering 95% of the width of the X band frequency), respectively. The results indicated that the microwave absorption performance of SrM could improve by mixing up its different morphologies types.