Improving the multiferroic properties and ability to absorb electromagnetic microwaves of NFO/BZT-BCT composites

Abstract

Multiferroic composites of xNiFe₂O₄/(1 − x)(0.5BaZr_0.2Ti_0.8O₃-0.5Ba_0.7Ca_0.3TiO₃) (NFO/BZT-BCT with x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) with an average particle size of 100 nm was prepared by high-energy ball milling combined with the thermal annealing methods. The X-ray diffraction patterns indicate the presence of both NiFe₂O₄ (NFO) and BaZr_0.2Ti_0.8O₃-Ba_0.7Ca_0.3TiO₃ (BZT-BCT) phases in the multiferroic composites. As the ferromagnetic phase content increases, the ferroelectric and ferromagnetic properties of the material are significantly improved. For an applied electric field below 10 kV cm⁻¹, the values of the residual polarization (P_r) and the coercive field (E_c) are found to be 0.02–0.064 μC cm⁻² and 2.06–5.67 kV cm⁻¹, corresponding to x = 0–0.8, respectively. The loss of energy density increases from 0.035 to 0.18 mJ cm⁻³ and the stored energy density decreases from 82.6 to 17.4%, with NFO content increasing from 0 to 0.8. The material has the ability to strongly absorb electromagnetic waves (EMW) in the frequency range of 2–18 GHz corresponding to thicknesses of 1.5–5 mm. With a thickness of 2.5 mm, the minimum reflection loss (RL_min) value reaches −41.87 dB occurring at 13.06 GHz for the NFO sample; RL_min = −38.51 dB for the BZT-BCT sample at 12.5 GHz and RL_min = −33.91 dB for the NFO/BZT-BCT with x = 0.4 (NBZ4) sample at 9.62 GHz. The research results show the potential for developing electromagnetic wave absorption applications of the material in a wide range of investigated frequencies from 2–18 GHz.