Investigation of structural, morphological, electromagnetic, reflection loss, and input impedance characteristics of co Cr substituted SrFe12O19/CoFe2O4 composites for microwave absorber application

In this communication, we prepared composites of Cobalt (Co) and Chromium (Cr) substituted strontium ferrite (Sr(CoCr) x Fe 12-2x O 19 ) with spinel ferrite (CoFe 2 O 4 ) at a 4:1 weight ratio, varying the substitution levels from x = 0.0 to 1.0. The X-ray diffraction analysis confirmed the presence of both hard (M-type) and soft (spinel) ferrite phases in the substituted composites, without any impurity phase. Fourier infrared spectroscopy identified two distinct absorption bands at 584 cm −1 cm −1 and 542 cm −1 , primarily associated with iron oxide, and a band at 409.6 cm −1 attributed to Co O bonds. Field emission scanning electron microscopy (FESEM) revealed hexagonal platelet-shaped particles alongside randomly oriented small spherical-shaped grains. Substitution improves the performance of microwave absorbers, such as reflection loss increased from x = 0.0 (−10.54 dB) to x = 1.0 (−29.60 dB, more than 90% absorption); −10 dB bandwidth of 1 GHz was observed in the x = 1.0 sample at thickness 8.1 mm. Composite x = 0.8 displayed a bandwidth-to-thickness ratio and percentage bandwidth of 3.4E-04 and 8.9% with 8.5 mm at 9.157 GHz frequency. Composite x = 0.8 showed the optimal values for Z real (1.091) and Z img (−0.054), resulting in the highest reflection loss (−29.92 dB) at 9.15 GHz with 8.5 mm thickness.