Microwave absorption properties of spinel-structured magnesium zinc aluminate nanocomposites through Mn doping: characterization and performance analysis of (Mg–Zn)_1−xMn_xAl₂O₄ (x = 0.05, 0.1, 0.15, and 0.2)

This research article investigates the microwave absorption properties of spinel-structured nanocomposites [(Mg–Zn)_1−xMn_xAl₂O₄ with x = 0.05, 0.1, 0.15, and 0.2] prepared through a sol–gel technique. Advanced analytical methods, including XRD, FESEM, FTIR, and UV–Vis spectroscopy, were employed to analyze the physical and structural characteristics of the prepared nanocomposites, which confirm the presence of ZnO, MgO, ZnAl₂O₄, MgAl₂O₄, and MnAl₂O₄ phases. FESEM reveals the spherical, rigid nanocrystal morphology with agglomeration. These nanocomposites display a bandgap ranging from 3.13 to 2.85 eV and exhibit varying dielectric properties and conductivities within the frequency range of 2–18 GHz. At x = 0.1 magnesium zinc aluminate exhibits a maximum reflection loss of −83.85 dB at 12.05 GHz with an effective absorption bandwidth (EAB) of 3.82 GHz, while the same sample shows the 4.82 GHz EAB at 5 mm thickness. Additionally, x = 0.05 nanocomposite at 5 mm thickness showed 4.32 GHz EAB with a maximum reflection loss of −71.35 dB at 14.91 GHz, and x = 0.15 nanocomposite showing an EAB of 4.16 GHz at 4.5 mm thickness. On the other hand, x = 0.2 nanocomposite shows the lowest EAB of 3.04 GHz at 7.5 mm thickness which covers both X and Ku bands.