Polarization Relaxation Research Articles

3D Lightweight Interconnected Melamine Foam Modified with Hollow CoFe2O4/MXene toward Efficient Microwave Absorption.

Considering the increasing severity of electromagnetic wave pollution, the development of high-performance low-filler-content microwave absorbers possessing wide frequency bands and strong absorption for practical applications is a demanding research hotspot. In this study, from the perspectives of the electromagnetic component coordination and structural design, a three-dimensional (3D) interconnected CoFe2O4/MXene-melamine foam (MF) was constructed via simple impregnation and a single freeze-drying step. By changing the absorber (CoFe2O4/MXene) concentration, the pore opening and electromagnetic properties of the 3D foams can be effectively adjusted. When the absorber concentration is sufficiently high to clog the internal pores, the microwave absorption is hindered. When the filler (CoFe2O4/MXene-MF) content is just ∼5.8 wt % (at a density of ∼33.3 mg cm-3), a minimum reflection loss (RLmin) of -72.1 dB is achieved at a matching thickness of 3.32 mm, and an effective absorption bandwidth (4.54 GHz) covering the whole X band is achieved at a thickness of 3 mm. CoFe2O4/MXene-MF, which possesses a 3D porous electromagnetic network structure, optimizes impedance matching and enhances multiple polarization relaxations and reflections/scattering, resulting in superior absorption capabilities. In particular, the continuous network structure ensures the uniform distribution of electromagnetic fields in the microstructure, achieving high absorption at low filler contents. This work provides a reference for subsequent 3D absorber concentration studies and a novel engineering strategy for preparing a low-filler-content, lightweight, and efficient electromagnetic wave absorber, which could be applied in the fields of radar security and information communications.

Effects of different atomic passivation on conductive and dielectric properties of silicon carbide nanowires

Based on the transport and polarization relaxation theories, the effects of hydrogen, fluorine, and chlorine atom passivation on the conductivity and dielectric properties of silicon carbide nanowires (SiCNWs) were numerically simulated. The results show that passivation can decrease the dark conductivity of SiCNWs and increase its ultraviolet photoconductivity. Among them, the photoconductivity of univalent (H) passivated SiCNWs is better than that of seven-valent (Cl, F) passivated SiCNWs. In terms of dielectric properties, the passivated SiCNWs exhibit a strong dielectric response in both deep ultraviolet and microwave regions. Hydrogen passivation SiCNWs produce the strongest dielectric response in deep ultraviolet, while fluorine passivation SiCNWs produce the strongest dielectric relaxation in the microwave band, which indicates that atomic passivation SiCNWs have a wide range of applications in ultraviolet optoelectronic devices and microwave absorption and shielding.

MOF derived α-Fe2O3/Ti3C2Tx magnetic-dielectric composites for microwave absorption

The design and development of microwave-absorbing materials with excellent performance hold significant importance in both civil and military fields. The combination of magnetic loss materials and dielectric loss materials can achieve complementary performance effects and regulate impedance matching. In this paper, spindle-like α-Fe2O3 was synthesized using MIL-88A as a template, which was then composited with Ti3C2Tx phase possessing excellent electrical conductivity to obtain Fe2O3/Ti3C2Tx composites. Ti3C2Tx can provide good conductance loss and dipole polarization relaxation, while the incorporation of Fe2O3 between the layers of Ti3C2Tx not only triggers the interfacial polarization effect but also increases layer spacing, thereby enhancing multiple reflection effects. Furthermore, the magnetic-dielectric synergies further optimize the impedance matching. Through the combined action of multiple mechanisms, the Fe2O3/Ti3C2Tx composites (with a mass ratio of 1:3 for Fe2O3 and Ti3C2Tx) exhibit a minimum reflection loss of −34 dB and an effective absorption bandwidth of 1.53 GHz at a thickness of 3 mm, as well as an effective absorption bandwidth of 2.805 GHz at a thickness of 1.5 mm. This paper presents a reference strategy for constructing highly efficient microwave absorbers derived from Metal-organic frameworks (MOFs) and MXene based on their outstanding properties.

Design and preparation of an epoxy resin matrix composite structure with broadband wave-absorbing properties

Aiming at the poor effect of broadband wave-absorbing, the structural wave-absorbing composites structure were designed and prepared by choosing FeNi alloy powder/epoxy nanocomposites as the wave-absorbing interlayer, and carbon fibers/epoxy composites as the structural materials. Firstly, “80 wt% Fe50Ni50 alloy powder/epoxy resin nanocomposites” were successfully prepared, with a density of about 2.4 g/cm3, which can be applied as wave-absorbing interlayer. Then, electromagnetic parameters and loss mechanisms of the wave-absorbing sandwich in the frequency band of 1–18 GHz were studied in detail. Finally, the radar wave absorption characteristics of the structural wave-absorbing composites were optimized. The study shows that the electromagnetic loss mechanism of wave-absorbing sandwich is dominated by conductive loss and eddy current loss in the frequency range of 1–6 GHz, and eddy current loss, resonant loss and relaxation polarization in the frequency range of 6–18 GHz. In the frequency band of 2.5–8 GHz, the angular tangent of the magnetic loss of the interlayer is tanδm ≥ 0.5, and, the attenuation constant is stabilized in the range of 160–180 in the frequency band of 5.2–13.2 GHz, which shows that the interlayer has a good capacity of electromagnetic wave absorption. Different wave-absorbing properties can be designed by changing the thickness of the wave-absorbing interlayer. And the “fiberglass/interlayer/carbon fiber” composite board with a thickness of 2.0 mm interlayer and 3.0 mm-thick “fiberglass/ epoxy” has excellent broadband wave-absorbing properties. The sandwich composites have wave-absorbing peaks of |RL|≥10 dB in the frequency bands of 4.93–8.79 GHz and 14.96–18.0 GHz, with the peak width of 6.90 GHz, and the absorption peak of |RL|≥54 dB.

Study of the relaxation time for the polarization mechanism in SiO2–SiC/B4C nanowires with broadband absorption of microwave

SiO2-supported SiC/B4C (SiO2–SiC/B4C) nanowires were synthesized by using SiO2@C nanospheres, amorphous B powders and catalyst Ni(NO3)2·6H2O as raw materials, and exhibited remarkable microwave absorbing characteristics. The minimum reflection loss of the SiO2–SiC/B4C nanowire/paraffin composite reaches −41.33 dB with an effective absorption bandwidth up to 9.69 GHz. The broadband microwave absorption of SiO2–SiC/B4C nanowires is attributed to the synergistic effect of interfacial polarization relaxation and conduction loss. While conductive loss dominates at low frequencies within 2–8 GHz, polarization loss caused by the heterogeneous interfaces plays an important role at high frequencies, especially between 10 and 16 GHz. The movement of the polarization relaxation peaks to lower frequencies in the composites is further investigated by modeling the relaxation process as a rotating sphere in a viscous fluid. The linear relationship between relaxation time and conductivity indicates that the conductivity is an important factor that affects the electromagnetic wave (EMW) absorption performance not only on the impedance matching and attenuation constant of the materials, but also regulates the relaxation time, and this result provides a new idea for exploring the absorption mechanism of EMW absorbing materials.

Influence of Bi doping on the structure and electromagnetic wave absorption for LaFeO3 perovskite

LaFeO3 perovskite has possessed great potential in the field of microwave absorption considering its outstanding dielectric and magnetic properties. In this work, Bi-doped LaFeO3 powders (BLFO) were prepared by a simple solid state reaction method. The results have demonstrated that the crystalline of LaFeO3 and the lattice oxygen are increased with the additionally introduced Bi. As a result, the samples could exhibit the strongest microwave absorption with the minimum reflection loss (RLmin) of −39.48 dB and the effective absorption band (EAB) of 3.63 GHz (10.28–13.91 GHz) at a filling ratio of 60 wt%. The excellent microwave absorption properties are ascribed to the enhanced conductive loss, polarization relaxation and the co-existed magnetic loss. Moreover, the optimum sample exhibits the radar cross-section values below −10 dBm2 across a wide angular range of −90° to 90° with a thickness of 2.5 mm. Therefore, this work opens up a feasible and effective way for modulating the electromagnetic properties of perovskite materials as potential microwave absorbents.

A comprehensive evaluation method for moisture and aging state of oil-immersed paper bushings based on dielectric modulus and K-nearest neighbor algorithm

The insulation performance of oil-immersed paper bushings is prone to deteriorate, primarily due to moisture intrusion and thermal aging. The frequency domain spectroscopy (FDS) method is commonly employed to assess the insulation condition of the bushing. However, identifying and extracting relaxation polarization information from the low-frequency region of the FDS curve can be challenging, and there is little research about the condition evaluation under the combined effects of aging states and moisture content. To address this issue, this article uses the Taylor formula mathematical model to extract characteristic parameters from the dielectric modulus curve of OIP bushings and uses the KNN algorithm to achieve the evaluation of aging and moisture status. Then, the effectiveness and accuracy of the proposed method are validated on three field OIP bushings. The results demonstrate that the evaluation accuracy of the proposed method exceeds 83%, which has significant advantages compared to other classification algorithms. The innovation of this article lies in extracting new feature parameters and combining them with intelligent classification algorithms to evaluate the moisture and aging state of the bushing.

Investigations on the optical, dielectric, electrical, and rheological properties of PEG200/ZnO semiconducting nanofluids for soft matter based technological innovations

Semiconducting nanofluids (SNFs) consisting of poly (ethylene glycol) (PEG200) as a green biocompatible base fluid with homogeneous dispersion of eco-friendly zinc oxide (ZnO) nanomaterial, concentrations ranging from 0.01 to 0.20 wt%, are prepared by state-of-the-art ultrasonic cavitation homogenized process. These PEG200/ZnO SNFs are characterized by employing an ultraviolet-visible (UV-Vis) spectrophotometer, precision inductance-capacitance-resistance (LCR) meter, and rotational viscometer. A detailed analysis of 200–800 nm range UV–Vis absorbance spectra of these SNFs revealed longer stability of suspended ZnO nanoparticles in PEG200 fluid, and their nanomaterial concentrations dependent absorbance and extinction coefficient with tunable dual energy band gaps ranging from 3 to 5 eV. Optical performance recognized the potential applications of these SNFs in the advances of soft matter based optoelectronic and photosensitive devices and also as an excellent UV radiation shielding material. The study of 20 Hz – 1 MHz range dielectric and electrical spectra explained that the ZnO concentrations have a significant impact on the electrical conductivity of these SNFs, while the dielectric permittivity and electrode polarization relaxation process are marginally altered. High static dielectric permittivity (∼ 22) and low electrical conductivity of about μS/cm order, at 303.15 K, evidence the suitability of these SNFs in advances of energy storage devices. The rheological behaviour of PEG200/ZnO materials is carried out at different temperatures ranging from 303.15 to 323.15 K, which illustrates the Newtonian characteristics of these nanofluids with moderate dynamic viscosity and activation energy, and therefore, they could be utilized as effective heat transfer materials in photovoltaic/thermal devices and systems.

Synthesis of nano/micro ternary magnetic particles with different Co content and their electromagnetic absorbing properties

To comprehend the influence of Co element content on the microwave absorption properties of FeCoNi alloy particles, five sets of nano/micro FeCoNi alloy particles with varying Co element contents were fabricated with chemical liquid deposition. The microstructure, static magnetic characteristics, and microwave absorption performance were studied. The results shown that the synthesized FeCoNi alloy particles exhibited spherical morphology and face-centered cubic crystal structure, with the average particle size increasing from 150 nanometers to 500 nanometers as the Co element content rose. All five sets of samples presented soft magnetic properties, with the saturation magnetization fluctuating between 97.1–129.5 emu/g and coercivity ranging from 40.4–280.3 Oe. As the frequency of electromagnetic waves increased, the real part of the complex permittivity of the alloy particles demonstrated minimal variation, while the imaginary part exhibited dielectric loss absorption peaks in the frequency ranges of 10–16 GHz, 10–14 GHz, and 8–10 GHz/13–16 GHz. The imaginary part of the complex permeability initially increased and then decreased with the frequency rose. All the samples exhibited distinct Debye semicircles and polarization relaxation losses within the samples. The sample with Co content of x = 0.8 Fe1Co0.8Ni1 achieved the maximum effective absorption bandwidth 5.36 GHz at thickness of 1.5 mm and the maximum reflection loss |RLmax| 32.5 dB at thickness of 2.2 mm for relatively good impedance matching and excellent combination of magnetic loss and dielectric loss.

Designing high-performance microwave absorption materials through co-doping strategy: Experimental and theoretical insights

The essence of designing ideal absorption materials is to control the electromagnetic parameters. In this work, doping strategy was adopted to regulate electromagnetic parameters. According to the experimental results and density functional theory calculations, the introduction of Co can make the charge redistribute, distortion increase, bonds length decrease, and bonds energy enhance, which can lead to the reducing of dielectric storage and raising of dielectric loss. Meanwhile, the superfine long nanowires of Co-doped MnO2 can bring abundant surface and interfaces, which improve the polarization relaxations. These changes result in the enhancement of attenuation and improvement of impedance matching feature at the same time. Therefore, the Co-doped MnO2 exhibits excellent microwave absorption performance, the minimal reflection loss is -51.03 dB and effective absorbing bandwidth can reach 7.04 GHz. This work offers an effective approach for the design of high-performance microwave absorption materials, which has been validated through experimental and theoretical evidence.

Molybdenum Based Manganese Oxides as Optoelectronic Nanomaterials: Synthesis, Structural & Optical Characterization

AbstractThis work reports the synthesis of molybdenum based manganese oxide nanomaterials named as (CH1‐CH5) via a facile hydrothermal approach. Nanomaterials were characterized through Powder XRD, SEM, BET, UV‐Vis, Photoluminescence, and FTIR analysis. Structural characterization revealed triclinic crystal structure of nanomaterials having particle sizes in the range of 23.08–52.7 nm with very low levels of microstrain levels (<0.05) and dislocation densities. Surface areas were found to be in the range of 42.37–52.32 m2/g with mesoporous structures and solid bar and cross surface morphology. Optical band gaps (Eg) calculated from absorption data was found to be in the range of 4.65–4.75 eV for direct transitions whereas 4.60–4.74 eV for indirect transitions. The Eg calculated from emission data was found to be in the range of 2.42–2.67 eV. Absorption edge broadening was investigated by urbach energy (EU) calculated to be in the range of 1.23–1.51 eV whereas fermi energy (Ef) were obtained as 4.66–4.72 eV. Refractive index (n) was calculated to be in the range of 0.13–0.21 whereas high values obtained for real and imaginary parts of dielectric constants (ϵ) indicating polarization relaxation in synthesized materials. The calculated structural and optical characteristics indicates that these materials can be potential candidates for optoelectronic and catalytic applications.

Divalent metal-ions blowing strategy achieved 3D luffa aerogels heterostructure for lightweight broadband microwave absorber

Explicitly, effective dispersion configuration and hierarchical network construction are two practicable measures to develop the broadband and lightweight absorbers. Based on the newly developed sugar blowing art, 3D Luffa aerogels heterostructure have been successfully developed through metal ion assisted caramel blowing (MCB) strategy. The Luffa foam hierarchical configuration with those dielectric, magnetic, and porous interfaces can be all achieved. Such hierarchical 3D lightweight aerogels are facilitated to building effective impedance matching networks (2.4 wt%) and exhibit an optimized polarization relaxation. Thus, the effective absorbing bandwidth (EAB) of the Luffa aerogel can be broadened up to 8.0 GHz. Moreover, the MCB strategy can be applicable to a wide range of divalent metal ions (Co2+, Ni2+, Mn2+, Zn2+ et al.). This study provides a new method for efficient synthesis of aerogel network structures and opens a way to realize lightweight and broadband electromagnetic wave absorbing (EWA) materials.

Synthesis of CoFe2O4/mesoporous-carbon hybrid nanocomposite with enhanced microwave absorption in K and Ka-band

In the present investigation, CoFe2O4/mesoporous-carbon nanocomposites were synthesized using a facile hydrothermal method and demonstrate their dual band (K and Ka-band) microwave absorption properties, where radiation from high-resolution and close-range radars, space telescopes, and wireless point-to-point microwave communication systems populates. XRD results confirmed the pure phase formation of CoFe2O4 nanoparticles. Vibrating sample magnetometer shows a decrease in magnetization value for CoFe2O4/mesoporous-carbon nanocomposites that can be attributed to the increasing contents of non-magnetic mesoporous carbon. The reflection loss of the hybrid nanocomposite reached −31 dB at a matching thickness of 2.5 mm and effective absorption bandwidth was 4.4 GHz. The enhanced microwave absorption properties derive from the synergistic effect amid dielectric and magnetic loss of mesoporous-carbon and ferrite, respectively, and better impendence matching at their interface. In addition, the dielectric loss can be associated with polarization relaxation and mesoporous carbon conductivity and the magnetic loss arises from the natural resonance of ferrite materials. The high reflection loss and wide absorption bandwidth display that CoFe2O4/mesoporous-carbon nanocomposite having admirable microwave absorption performances can be a capable candidate for stealth technology and in advanced communication systems.

Dynamically tunable multi-band plasmon-induced absorption based on multi-layer borophene ribbon gratings.

In this paper, we propose a borophene-based grating structure (BBGS) to realize multi-band plasmon-induced absorption. The coupling of two resonance modes excited by upper borophene grating (UBG) and lower borophene grating (LBG) leads to plasmon-induced absorption. The coupled-mode theory (CMT) is utilized to fit the absorption spectrum. The simulated spectrum fits well with the calculated result. We found the absorption peaks exhibit a blue shift with an increase in the carrier density of borophene grating. Further, as the coupling distance D increases, the first absorption peak shows a blue shift, while the second absorption peak exhibits a red shift, leading to a smaller reflection window. Moreover, the enhancement absorption effect caused by the bottom PEC layer is also analyzed. On this basis, using a three-layer borophene grating structure, we designed a three-band perfect absorber with intensities of 99.83%, 99.45%, and 99.96% in the near-infrared region. The effect of polarization angle and relaxation time on the absorption spectra is studied in detail. Although several plasmon-induced absorption based on two-dimensional (2D) materials, such as graphene, black phosphorus, and transition metal dichalcogenides (TMDs), have been previously reported, this paper proposes a borophene-based metamaterial to achieve plasmon-induced perfect absorption since borophene has some advantages such as high surface-to-volume ratios, mechanical compliance, high carrier mobility, excellent flexibility, and long-term stability. Therefore, the proposed borophene-based metamaterial will be beneficial in the fields of multi-band perfect absorber in the near future.

High-frequency resolution diamond nitrogen-vacancy center wide-spectrum imaging technology

High-resolution wide-spectrum measurement techniques have important applications in fields such as astronomy, wireless communication, and medical imaging. Nitrogen-vacancy (NV) center in diamond is well known for its high stability, high sensitivity, real-time monitoring, single-point detection, and suitability for long-term measurement, and has an outstanding choice for spectrum analyzers. Currently, spectrum analyzers based on NV centers as detectors can perform real-time spectrum analysis in the range of several tens of gigahertz, but their frequency resolution is limited to a MHz level. In this study, we construct a quantum diamond microwave spectrum imaging system by combining continuous wave-mixing techniques. According to the spin-related properties of the NV center in diamond, we implement optical pumping by 532 nm green laser light illuminating the diamond NV center. A spherical magnet is used to produce a magnetic field gradient along the direction of the diamond crystal. By adjusting the size and direction of the magnetic field gradient, spatial encoding of the resonance frequency of the NV center is achieved. The magnetic field gradient induces the Zeeman effect on the diamond surface at different positions, generating corresponding ODMR signals. Through accurate programming, we coordinate the frequency scanning step size of the microwave source with the camera exposure and image storage time, and synchronize them circularly according to the order of image acquisition. Ultimately, after algorithmic processing, we successfully obtain comprehensive spectrum data in a range from 900 MHz to 6.0 GHz. Within the measurable spectrum range, the system employs continuous wave-mixing, simultaneously applying resonant microwaves and slightly detuning auxiliary microwaves to effectively excite the NV center. This method triggers off microwave interference effects, disrupting the balance between laser-induced polarization and microwave-induced spontaneous relaxation. Specifically, microwave interference causes the phase and amplitude of the fluorescence signal to change, leading to the generation of alternating current fluorescence signals. This further enhances the response of the NV magnetometer to weak microwave signals. The method enables the system to achieve a frequency resolution of 1 Hz in the measurable spectrum range, and it can separately measure the frequency resolution of multiple frequency points with a frequency step size of 1 MHz. The research results indicate that the wide-spectrum measurement based on NV centers can achieve sub-hertz frequency resolution, providing robust technical support for future spectrum analysis and applications.

Investigation of variable range hopping and dielectric relaxation in GdCrO3 orthochromite perovskites.

This study investigates the structural, electrical, and dielectric properties of GdCrO3 (GCO) compounds. X-ray diffraction analysis confirmed the formation of the perovskite phase of GCO, crystallizing with the Pbnm space group. Scanning electron microscopy (SEM) was employed to examine the morphology and chemical composition of the powder, ensuring compound homogeneity, while transmission electron microscopy (TEM) provided insights into the internal structure and finer morphology of the GCO sample. Electrical measurements revealed that GCO exhibits semiconductor behavior, with a notable increase in conductivity as temperature rises, attributed to enhanced charge carrier mobility and hopping conduction mechanisms. Dielectric analysis demonstrated significant frequency-dependent behavior, characterized by various polarization effects and relaxation phenomena. GCO is a promising material for energy storage due to its giant permittivity and low energy loss. The activation energies derived from the electrical and dielectric measurements indicate higher resistance within the grains compared to the grain boundaries, suggesting complex conduction processes. Additionally, the dielectric loss spectra revealed substantial losses, likely due to defect states such as oxygen vacancies and mixed valence states, indicating a highly disordered material. These comprehensive insights into the structural and functional properties of GCO highlight its potential applications in electronic and electrical devices where controlled conductivity and dielectric properties are crucial.

Oxygen vacancy redistribution and ferroelectric polarization relaxation on epitaxial perovskite films during an electrocatalytic process

Ferroelectric catalysis BaTiO3 films show negative ferroelectric polarization drives the oxygen vacancies redistribution to the surface accelerating the adsorption of reactants and charge transfer, resulting in an enhanced OER performance.

Scalable High‐Permittivity Polyimide Copolymer with Ultrahigh High‐Temperature Capacitive Performance Enabled by Molecular Engineering

AbstractPolymer capacitors are essential components of advanced electronic and power systems. However, the deficient high‐temperature capacitive performance of polymer dielectrics fails to meet the demand for harsh condition applications, due to the mutually restrictive relationships in permittivity (εr), glass transition temperature (Tg), and bandgap (Eg). Here, a modularized molecular engineering strategy is reported to enhance the high‐temperature capacitive performance of polymer dielectrics. First, the potential influences of multiple structural units on εr, Tg, and Eg of polymers are elucidated by comparing a set of polyimides (PIs). After screening out an excellent sulfonated PI with concurrently high εr (4.2), Eg (3.4 eV), and Tg (311.2 °C), a semi‐alicyclic sulfonyl‐containing PI copolymer is further synthesized that exhibits a superior discharged energy density of 4.3 J cm−3 above 90% efficiency at 200 °C and 485 MV m−1. Density functional theory calculations demonstrate that the combination of polar sulfonyl group, ether linkage, and alicyclic group in the backbones of the copolymer decouples the dipole orientation and the segmental motion of backbones, and reduces conjugation effects of aromatic groups, thereby minimizing the polarization relaxation loss and the conduction loss while retaining excellent thermal stability and high permittivity.

The MOFs/COFs-derivant decorating FeSiAl coupling magnetic and electrical losses for enhanced microwave absorption

Traditional single-component microwave absorbers face the difficulties including the narrow absorption bandwidth and low absorption strength. Herein, we develop a novel dual-magnetic composite decorating with covalent-organic framework (COF of 1,3,5-triformylphloroglucinol and p-phenylenediamine: TpPa) and carbon hybrid to enhance microwave absorption performance. Namely, a dual-magnetic FeSiAl@(CoFe2O4/C)@TpPa core–shell structure with rich interfacial polarizations was prepared by the three main steps: firstly, the plate-like FeSiAl was decorated with the MOFs of ZIF-67. And then it was converted to FeSiAl@(CoFe2O4/C) after an annealing process under Ar. Lastly, the in-situ growth of COF (TpPa) was designed for enhanced microwave penetration into the interior of absorbers. The as-design dual-magnetic FeSiAl/CoFe2O4 effectively favors to magnetic domain resonance resulting in the dual-magnetic coupling effects. Meanwhile, the multi-level structure formed by ultra-fine carbon in FeSiAl@(CoFe2O4/C)@TpPa enables magnetic-dielectric synergies and enriches the attenuation path as well. Furthermore, the accumulation of transferred charge at multiple interfaces provides a stronger relaxation polarization loss. The above positive factors collectively promote the high-performance microwave absorption with the reflection loss (RL) value up to −51.3 dB and the effective absorption bandwidth (EAB) covers 3.2–17.7 GHz by adjusting the thickness of absorbers. Therefore, this dual-magnetic/dielectric coupling approach provides an innovative strategy for fabricating advanced microwave absorbers.

Modulation effect of Zr-Sm co-doped on microwave absorption performance of barium ferrite

Zr-Sm co-doped barium ferrites BaFe12–2x(ZrSm)xO19(x = 0, 0.2, 0.4, 0.6) were successfully prepared by sol-gel method. The effects of Zr-Sm co-doped on phase formation, microscopic morphology, magnetic parameters, electromagnetic and microwave absorption properties of barium ferrite were studied. The results show that the saturation magnetization(Ms) of BaFe12–2x(ZrSm)xO19 first increases and then decreases, the coercivity(Hc) first decreases and then increases with the increase of doping amount(x) of Zr-Sm. Large grain size and sheet morphology lead to the transition of BaFe11.6(ZrSm)0.2O19 towards soft magnetic properties. The introduction of Zr-Sm increases the amount of oxygen vacancies, and dielectric loss value of material is obviously enhanced, this improves the polarization relaxation of materials. At the same time, multiple natural resonance peaks appeared in the virtual part of the permeability (μ"), which regulated the absorbing properties of samples. The best microwave absorption properties of sample is obtained when doping x = 0.2, at the thickness of 2.8 mm, the maximum reflection loss(RL) is − 51.75 dB. The effective absorption bandwidth (RL ≤ −10 dB) is 4.4 GHz, it covers almost all the X-band(8–12 GHz). Compared with existing doped barium ferrite, the material possesses a greater reflection loss and excellent prospects in the field of microwave absorption.