Optimization of electromagnetic matching of carbonyl iron/BaTiO3 composites for microwave absorption

Microwave absorbing materials filled with BaTiO₃ and carbonyl iron (CI) particles with various weight fractions (BaTiO₃/CI particles=100/0 to 0/100) are investigated. The dielectric and magnetic properties of the absorbers can be tuned by changing the weight ratio of BaTiO₃/CI particles in the frequency range of 2-18 GHz. Numerical simulations are also performed to design a single-layer and double-layer absorber. The minimum reflection loss of the composite filled with 20 wt% BaTiO₃ and 60 wt% CI particles at 2.0 mm thickness can be reached to −42 dB at 4.1 GHz. With the weight ratio of CI particles in the composite increased, the microwave absorption peak shifted to the lower frequency region. By using a double-layer absorber structure, the microwave absorption performance of the absorber is enhanced. The result shows that the total thickness of the absorber can be reduced below 1.4 mm by using a matching layer filled with 50 wt% BaTiO₃, and an absorption layer filled with 60 wt% BaTiO₃ and 20 wt% CI particles, whereas the reflection loss below −10 dB can be obtained in the frequency range of 10.8-14.8 GHz and the minimum reflection loss of −59 dB can be obtained at 12.5 GHz.