Enhanced Microwave Absorption Properties of Double-Layer Absorbers Based on Spherical NiO and Co0.2Ni0.4Zn0.4Fe2O4 Ferrite Composites

Microwave absorption properties of spherical NiO particles and Co0.2Ni0.4Zn0.4Fe2O4 (CNZF) ferrites with single-layer and double-layer absorbers were studied in the frequency range of 2–18 GHz. The spherical NiO particles were synthesized by using a hydrothermal process, while the CNZF powders were prepared by using a sol–gel autoignition method. The double-layer absorbers, composed of 30 wt% NiO as matching layer and 30 wt% CNZF as absorption layer, with a total thickness of 3.2 mm, exhibited a maximum reflection loss (RL) of –67.0 dB at 9.2 GHz and an effective absorbing bandwidth below –10 dB to be 3.9 GHz from 7.0 to 10.9 GHz. The excellent microwave absorption performance of the double-layer absorbers should be ascribed to the high impedance matching ratio, the great microwave attenuation capability, and well-coupled layer.