Search

This paper is aimed at acquiring functional ceramics with broadband magnetoelectric (ME) response for sensing wide-range of dc bias magnetic field. Three-phase particulate ceramics CoFe2O4/Ni0.8Zn0.2Fe2O4/Bi0.5Na0.4K0.1TiO3 (CFO/NZFO/BNKT) were fabricated, and the effect of magnetostrictive phase on the piezoelectric, magnetic, and ME properties were investigated systematically. Separated phases and homogeneous microstructure of the magnetostrictive and piezoelectric phases were confirmed. The variation in magnetostrictive coefficient with dc magnetic field was found to be markedly dependent on the relative content of magnetostrictive microparticles. By merging the nonlinear piezomagnetic response of the two ferrite components together, the ME composites present dual-peak bands. A wide-range ME coefficient was achieved over a magnetic range of 1800 Oe with large ME value of 20 mV/cm Oe. This field-conversion broadband ME behavior indicates that three-phase particulate ME ceramics are quite preferable for practical applications in magnetic field sensor. [ABSTRACT FROM AUTHOR]

• Shell-core structured C@Ni 0.5 Zn 0.5 Fe 2 O 4 nanoparticles have been successfully synthesized by the tannic acid coating method. • Minimum reflection loss of the C@Ni 0.5 Zn 0.5 Fe 2 O 4 –5:1–900℃ sample is −26.87 dB at 4.3 GHz, and the effective absorption bandwidth is 4.05 GHz. • Microwave absorption performance can be controlled by adjusting the annealing temperatures and shell-core mass ratios. • The microwave attenuation mechanisms are discussed in detail. C@Ni 0.5 Zn 0.5 Fe 2 O 4 nanoparticles with different annealing temperatures and shell-core mass ratios were synthesized by a tannic acid coating method. Through SEM, TEM, EDS and XRD characterization, the as-prepared product was confirmed to be shell-core structured C@Ni 0.5 Zn 0.5 Fe 2 O 4 nanoparticles with an average diameter of approximately 650 nm, and a carbon layer was deposited on the surface of the product. Compared with uncoated NiZn ferrite, the carbon-coated NiZn ferrite exhibits a moderate real part and imaginary part of its complex permittivity, while maintaining high permeability, which improves the impedance matching characteristics and microwave loss performance of the material. When the shell-core mass ratio was 9:1 and the annealing temperature was 900 °C, the as-prepared sample exhibited advanced microwave absorption performance with a minimum reflection loss (RL) of -26.87 dB at 4.3 GHz with a matching thickness of 1.8 mm, and the effective absorptive bandwidth was approximately 4.05 GHz when the RL was below -10 dB. [Display omitted] [ABSTRACT FROM AUTHOR]

An optimized NiZn ferrite absorber for the whole P-band (230 -1000 MHz) is proposed by inserting cross-shaped metamaterial. Effective absorption bandwidth below − 10 dB for the composite absorber covers the frequency range 210 MHz-1000 MHz. Electromagnetic wave attenuation mechanisms are revealed by surface current distribution and power loss density distribution. The increased absorption bandwidth of the composite absorber is attributed to the overlap effect of three absorption peaks originated from the multilayer cross-shaped metamaterial absorbers. Results indicate that the proposed composite absorber can be utilized in the P-band with relatively less thickness compared to the traditional NiZn ferrite absorber. [ABSTRACT FROM AUTHOR]

Recent progress in exploring and developing new microwave absorbing materials is highlighted. In this paper, we reported on microwave electromagnetic properties of the novel quaternary ferrite La-substituted Ba 12 Fe 28 Ti 15 O 84 prepared via a modified sol-gel method. A systematic study was conducted to identify the effects of La substitution on structure, conductive, dielectric, magnetic and microwave absorbing properties. The modified samples had a monoclinic crystal structure and exhibited dense plate-like grains. The introduction of La into Ba 12 Fe 28 Ti 15 O 84 had a remarked influence on conductive behavior, dielectric and magnetic properties and in turn provided the tunable microwave electromagnetic properties. A significant enhancement of reflection loss (RL) was observed for the Ba 12- x La x Fe 28 Ti 15 O 84 (x = 3) sample, showing a broadened absorption bandwidth (RL < -10 dB) covering the nearly X-band. In addition, microwave absorption mechanism of the doped ceramics was discussed. • Single-phase Ba 12 Fe 28 Ti 15 O 84 samples were prepared by a modified sol-gel method. • The introduction of La into Ba 12 Fe 28 Ti 15 O 84 enhances the magnetic properties and improves impedance matching characteristic. • A significant enhancement of microwave absorption property was observed for the doped Ba 12 Fe 28 Ti 15 O 84. [ABSTRACT FROM AUTHOR]