Optimization of Electromagnetic Matching of Carbonyl iron / La0.8Sr0.2MnO3 Composites for Microwave Absorption

In the present research the nano- sized La0.8Sr0.2MnO3 (LSMO) powder was synthesized using a simple sol-gel method. Microwave absorbing materials consisting of 80wt% carbonyl iron (CI) particles and LSMO with different proportions of CI: LSMO being 80:0, 79:1, 77:3, 74:6, and 72:8, respectively, and 20wt% molten wax are investigated in the frequency range of 8-12 GHz. The composite materials in the form of paints were applied on an aluminum substrate (22.8×10.1×0.8 mm3) with the thicknesses of 0.7, 0.9 and 1.1 mm, respectively. Phase analyses and crystallite size of the LSMO powder, morphology of particles, and the electro–magnetic (EM) absorption properties (8-12 GHz) of the paints were determined using X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FE-SEM), and vector network analysis (VNA), respectively. The composite with a CI/LSMO ratio of 74:6 showed an optimal reflection loss of –10.89 dB at 11.55 GHz with a matching thickness of 0.9 mm. By increasing the thickness of coating from 0.7 to 1.1 mm, the average absorption properties were increased. Therefore, CIP/LSMO composites were characterized as super-thin electromagnetic absorbers with a wider absorption bandwidth in GHz frequency bands.