Electromagnetic wave absorption properties of Ni0.5Zn0.5Fe2O4–BaTiO3–epoxy composites

Abstract

Composites consisting of ferrimagnetic spinel ferrite Ni0.5Zn0.5Fe2O4 (ZNF) and ferroelectric BaTiO3 (BT) powders embedded in epoxy (10 wt%) were synthesized and analyzed for their electromagnetic (EM) wave absorption properties. The ZNF and BT powders were combined in weight ratios of 1-x: x, where x = 0, 0.1, 0.2, 0.3, 0.4, and 1.0. With increasing x, the height of the complex permittivity (ε′ and ε″) spectra increased, while the height of the complex permeability (μ′ and μ″) spectra gradually decreased. The reflection loss (RL) value, indicative of EM absorption efficiency, was calculated using measured ε′, ε″, μ′, and μ″ data. Apart from the BT–epoxy sample (x = 1.0), which exhibited no magnetic loss mechanisms, the EM wave absorption characteristics in the NZF-BT-epoxy composites were predominantly influenced by magnetic loss mechanisms, as reflected in the μ″ values. The incorporation of BT modified the impedance matching conditions, causing the frequency at which maximum EM wave absorption indicated by the minimum RL (RLmin) occurs to shift to lower frequencies. The most remarkable EM wave absorption performance was observed for the sample with x = 0.4, where RLmin reached −70 dB. Notably, the samples with x values ranging from 0 to 0.4 demonstrated outstanding EM wave absorption capabilities within the radar frequency range of L and S-bands (1–4 GHz). Furthermore, the EM wave absorption bandwidth (Δf), representing the frequency range where RL < -10 dB, was 8.3 GHz (4.5–12.8 GHz) for the x = 0 sample. However, this bandwidth decreased to 2.6 GHz (5.0–7.6 GHz) for the x = 0.4 sample. Although the addition of BT led to a reduction in the EM wave absorption bandwidth compared to the NZF–epoxy composite (x = 0), it enabled the tuning of the absorption band towards lower frequencies, particularly emphasizing excellent EM wave absorption in the L-band.