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The Dy2Co17 compound series has garnered considerable attention due to its high saturation magnetization and Curie temperature, making it a promising candidate for microwave absorption applications. The ideal electromagnetic wave absorbing material should possess exceptional electromagnetic wave attenuation and optimal impedance matching. Doping the material can improve its electromagnetic wave attenuation and impedance matching value, thereby enhancing its electromagnetic wave absorbing ability. In this study, Dy2Co17−xNix samples were designed to increase their attenuation capability. The addition of Ni elements caused lattice distortion, which modulated the relaxation polarization and resonance loss capability, resulting in the best impedance matching value. The data on attenuation constant, impedance matching value, electromagnetic parameters, magnetism, eddy current loss, and reflection loss of Dy2Co17−xNix were investigated and analyzed. The results revealed that the samples have a plate-like morphology, and at a frequency of 7.12 GHz and a thickness of 2 mm, the RLmin of Dy2Co16.7Ni0.3 reached − 44.50 dB, indicating good impedance matching. Furthermore, based on CST simulation, the samples demonstrated an effective reduction in the RCS value, highlighting its excellent electromagnetic wave attenuation ability. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDH) are employed as a promising template to prepare magnetic polymetallic alloys with hierarchical or hollow structure, being regarded as the promising candidates for the lightweight and high-performance electromagnetic wave (EMW) absorption materials. However, the application of LDH-derived magnetic alloys in EMW absorption is still limited by the single loss mechanism and poor impedance matching properties. Coupling with dielectric materials is a viable strategy to solve the issue. Herein, flower-like hierarchical FeNi@C microspheres are fabricated by pyrolysis of FeNi-LDH precursors, which display excellent EMW absorption performance. Good impedance matching and strong absorption capability of the FeNi@C microspheres can be realized by regulating the phase composition and microstructure under different pyrolysis temperatures. When pyrolyzed at 700 °C, the FeNi@C microspheres exhibit a strong reflection loss (RL) of −30.4 dB with ultra-thin matching thickness of only 1.2 mm, achieving the widest effective bandwidth (RL < −10 dB) of 4.6 GHz at 1.4 mm. The superior EMW absorption performance of the FeNi@C-700 sample is ascribed to the synergistic effects of hierarchical structure with multiple reflection, FeNi particles with magnetic loss and carbon matrix with dielectric loss. Thus, the as-obtained FeNi@C microspheres can be a prospective lightweight EMW absorber. This work can also provide guidance for design and development of hierarchical LDH derivatives in EMW absorption. [Display omitted] • Flower-like FeNi@C microspheres were prepared. • FeNi nanoparticles were coated by carbon matrix to form the petals. • The minimum reflection loss achieved −30.5 dB at 1.2 mm. • The widest bandwidth was 4.6 GHz at 1.4 mm. • The performances were due to synergistic effects of components and structure. [ABSTRACT FROM AUTHOR]

The crystal structure, magnetic, and microwave absorption properties of the (Nd1−xLax)2Fe14B system have been investigated. The La2Fe14B compound was successfully synthesized and refined, giving a tetragonal structure, space group P42/mnm with the Nd2Fe14B-type structure. The crystal structure parameters of the (Nd1−xLax)2Fe14B compounds were determined by full-profile Rietveld refinements. The results revealed that all intermediate alloys form a continuous solid solution. The normalized lattice parameters of the (Nd1−xLax)2Fe14B compounds increase linearly with an increase of La concentration. Based on the results of DSC measurements and X-ray powder diffraction examinations, the phase diagram of the Nd2Fe14B-La2Fe14B system has been constructed. The remanence (Mr) and coercivity (Hc) of (Nd1−xLax)2Fe14B (x = 0.00, 0.10, 0.20, 0.30, and 0.40) gradually decrease. The highest reflection loss is − 29.8, − 27.4, − 24.1, − 18.6, and − 14.2 dB at 9.8, 8.9, 7.5, 6.9, and 6.5 GHz, respectively. The absorption peak shifts toward from higher frequency region to lower frequency region and the absorption bandwidth widens with the increase of the La substitution. [ABSTRACT FROM AUTHOR]

Functional core-shell heterostructure, which can integrate the characteristics of multiple components to achieve synergistic effects, have been widely explored in electromagnetic wave (EMW) absorption materials. In this work, core-shell ZnO@ZnO/FeNi microrods (MRs) derived from ZnO@ZnFeNi hydroxide (ZnFeNi OH) are prepared by a simple hydrothermal reaction and subsequent pyrolysis process. The introduction of FeNi alloy helps to optimize the impedance matching of ZnO, thus improving the EMW absorption performance. The different impedance matching properties of core-shell ZnO@ZnO/FeNi MRs are realized by adjusting the ZnO/FeNi shell thickness by changing the hydrothermal reaction time. When the hydrothermal time is 10 h, the core-shell ZnO@ZnO/FeNi MRs supplies the optimal EMW absorption performance with the minimum reflection loss of −53.7 dB and the widest absorption bandwidth of 5.3 GHz at a filler content of 33%. The synergistic effect of ZnO–FeNi interfacial polarization and the strong dielectric-magnetic loss are responsible for its superior EMW absorption performance. This work provides a valuable strategy for constructing core-shell dielectric@ magnetic composites to obtained high efficiency absorber. [ABSTRACT FROM AUTHOR]

• BaFe 12 O 19 /CeO 2 composites were prepared by solid-state reaction method. • BaFe 12 O 19 is a high magnetic ferrite and CeO 2 is a dielectric semiconductor. • The minimum reflection loss achieved − 51.2 dB. • The absorption ability was improved due to the synergistic effects of BaFe 12 O 19 &CeO 2. Hexagonal barium ferrite (BaFe 12 O 19) is a promising microwave absorption material, due to high magnetic loss and stable chemical state. However, the poor electrical performance of BaFe 12 O 19 will lead to impedance mismatch and poor absorption capacity. Compounding with other dielectric materials is a feasible way to solve the above problems. In this work, BaFe 12 O 19 + x% CeO 2 (x = 0, 0.16, 0.31, and 0.64) were prepared by conventional solid state reaction method. The microwave absorption performance of BaFe 12 O 19 /CeO 2 composites was significantly improved in comparison with single BaFe 12 O 19 , which is mainly correlated with the synergistic effects of magnetic loss, dielectric loss and multiple reflections. The x = 0.31 sample exhibited the minimum reflection loss of − 51.2 dB at 6.5 GHz and bandwidth with the loss above 10 dB is about 2.7 GHz. In addition, when x = 0.64, the reflection loss of - 23.6 dB could be achieved at only 1.8 mm and effective bandwidth is 3 GHz. Consequently, the facile preparation pathway and excellent performance make BaFe 12 O 19 /CeO 2 composite a promising candidate for efficient low-frequency electromagnetic wave absorbing. [ABSTRACT FROM AUTHOR]

Element substitution is an important means of preparing high-performance microwave absorbing materials by adjusting their physicochemical properties. The sol-gel method is employed as the primary technique in this study to synthesize a range of Ca 2- x La x Fe 2 O 5 (x = 0, 0.1, 0.2, 0.3) iron oxide materials by regulating the quantity of La element added. The Ca 1.8 La 0.2 Fe 2 O 5 has a minimum reflection loss (RL min) of −41.64 dB at a thickness of 2.2 mm, with an effective absorption bandwidth (EAB, RL ≤ −10dB) of 3.36 GHz. At an ultra-thin thickness of 1.8 mm, the RL min ＝－35.62 dB, and the effective absorption bandwidth is 4.48 GHz (almost occupying the entire Ku band). Ca 1.8 La 0.2 Fe 2 O 5 has the potential to become a new high-performance microwave absorbing material. The electromagnetic (EM) simulation results show that the sample had excellent radar cross-section reduction ability over a wide range of incident angles. This work provides guidance and ideas for the design and application of Ca 2 Fe 2 O 5 in electromagnetic wave (EMW) absorption. [ABSTRACT FROM AUTHOR]

LaNiO 3 is considered electromagnetic wave-absorbing material owing to its unique crystal structure and controllable dielectric constant. However, the effect of ion doping modification on microwave absorption performance remains to be thoroughly investigated. In this study, LaNi 1− x Ba x O 3 (x = 0, 0.02, 0.04, 0.06) was prepared through sol-gel methods. The reflection loss (RL) of the sample in the 2−18 GHz band was calculated using transmission line theory. Specifically, LaNi 0.96 Ba 0.04 O 3 exhibited superior results, with an RL value of −34.54 dB at d = 3 mm and f = 6.80 GHz, indicating effective absorption within the C-band. These results suggest that adding an appropriate amount of Ba ions to the material can effectively regulate the electromagnetic parameters and optimize impedance matching. Introducing Ba ions into the crystal interior produces abundant defects, which provide active sites for multipolarization and ultimately improve the wave-absorbing properties of the material. In addition, radar cross section(RCS) simulations simulation after coating the samples on original ideal conductor (PEC) substrates provide support for potential practical applications of the material. [ABSTRACT FROM AUTHOR]

In this paper, a high-purity NdFe 1-x Ni x O 3 perovskite-type material was prepared by a simple sol method. At the same time, adjust the substitution content of nickel to achieve the purpose of adjusting the dielectric properties and magnetic properties. According to the respective instruments, as Ni is substituted into the NdFeO 3 , the crystal microstructure will change to a certain extent, and there is a certain causal relationship between the magnetic properties and the bonding. Therefore, by adding a certain amount of nickel, the dielectric properties and magnetic properties can be adjusted to a certain balance point. NdFe 1-x Ni x O 3 material has excellent microwave absorption performance. When x = 0.2, the minimum reflection loss value is −49.32, and the corresponding impedance matching value is 1, and the effective bandwidth is 2.2 GHz when the thickness is 5.0 mm. The material that adjusts the perovskite structure by Ni element is beneficial to make the microwave absorption peak move from high frequency to low frequency, which has a wider application range and is closer to civil, commercial, military and aerospace. [ABSTRACT FROM AUTHOR]

In this study, porous Ce-doped CaFe 0.5 Mn 0.5 O 3–δ (CFMO) with good microwave absorption properties is reported for the first time. Herein, Ce x Ca 1−x Fe 0.5 Mn 0.5 O 3−δ (x = 0, 0.05, 0.1, 0.15) (Ce-CFMO) sample powders were prepared by sol–gel method after calcination at 750 °C. Ce-CFMO was characterized by XRD, SEM, TEM, XPS, and VSM, and the Ce-CFMO was also mixed with paraffin wax for VNA. The addition of Ce led to enhanced porosity, enhanced interfacial polarization, enhanced defect polarization, and higher oxygen vacancy content in the CFMO. This resulted in enhanced charge polarization and dipole polarization as well as significant optimization of the impedance matching of CFMO. The unique pore structure of the CFMO is the main reason for its microwave absorption performance. Moreover, the preparation method of this material is simple and its cost is low, providing it with wide application prospects. CFMO has not yet been applied in the field of microwave absorbing materials, and there is still a lot of room for development in the future. [ABSTRACT FROM AUTHOR]

Y 2 O 3 has emerged as a promising material for electromagnetic wave (EMW) absorption due to its excellent dielectric properties. However, the inherent insulating nature and single loss mechanism limit its absorption performance. Research on the microstructure modulation and component regulation of Y 2 O 3 -based absorbers remains relatively unexplored. In this work, Y 2 O 3 /C composites with flower-like architectures were synthesized for the first time via a metal-organic framework (MOFs) templating method. The effects of pyrolysis temperature on the microstructure, phase composition, and EMW absorption performance of the Y 2 O 3 /C composites were systematically investigated. At a pyrolysis temperature of 800 °C, the flower-like Y 2 O 3 /C microsphere exhibited optimal EMW absorption performance. The minimum reflection loss (RL) of pristine Y 2 O 3 was only −4.75 dB, while the Y 2 O 3 /C composite achieved a minimum RL of −51.77 dB and a maximum effective absorption bandwidth of 4.32 GHz. Moreover, by simply adjusting the matching thickness, the optimal sample exhibited strong absorption (RL < −30 dB) over a wide frequency range of 4–18 GHz. The incorporation of carbon effectively neutralized the insulating nature of Y 2 O 3 , thereby optimizing the impedance matching. The synergistic effects of multiple loss mechanisms, including polarization loss, resistance loss, and interfacial polarization, facilitated substantial EMW attenuation. This study provides a promising strategy for the design and fabrication of high-performance rare-earth oxide EMW absorbers with tunable morphologies and properties. • The Y 2 O 3 /C composites are derived from Y-MOF-74. • Y 2 O 3 /C composites have a stable flower-like structure. • The strong reflection loss is −51.77 dB and the widest bandwidth is 4.32 GHz. • The impedance matching plays a determining role in Electromagnetic wave absorption. [ABSTRACT FROM AUTHOR]

• Preparation of BaFe 12 O 19 and SmFeO 3 composite by sol–gel method. • Use the henkel diagram, the reciprocal curve of the hysteresis loop and the maximum magnetic energy product to explain the magnetic properties of the BaFe 12 O 19 @SmFeO 3 composite. • The addition of SmFeO 3 moves the microwave absorption frequency of the BaFe 12 O 19 @SmFeO 3 composite to low frequency. • While BaM + SmFeO 3 15% has the best absorbing performance, there are two reflection loss peaks, the maximum reflection loss is −48.5 dB, the bandwidth is 3.4 GHz. In this study, BaFe 12 O 19 (BaM)/SmFeO 3 10%, 15 %, and 20 % were synthesized via the sol–gel method. SmFeO 3 was uniformly attached to the BaM surface in the prepared composite. As the SmFeO 3 content increases, the weak magnetic properties of SmFeO 3 caused a gradual decrease in the saturation magnetization of the composite and a gradual increase in its coercive force. Based on the Henkel diagram, an exchange coupling between the two magnetic phases is observed. Similarly, the high permeability of BaM and the best dielectric properties of SmFeO 3 together improved the microwave absorption performance of the composite. The maximum reflection loss and bandwidth of BaM/15 %SmFeO 3 reached −48.5 dB and 3.4 GHz, respectively. [ABSTRACT FROM AUTHOR]

• PrFeO 3 ceramics were prepared by the solid-state reaction method and the sol–gel method. • The magnetic properties of PrFeO 3 ceramic have obviously changed from antiferromagnetic to ferromagnetic by increasing the annealing temperature and time. • Possible mechanisms of structure, magnetic and microwave absorption properties have been analyzed. To investigate the magnetic and microwave absorption properties of PrFeO 3 ceramic, the traditional solid-state reaction and sol–gel methods were used. The results show that only an orthorhombic crystal structure was detected by X-ray diffraction and transmission electron microscopy. Interestingly, heat treatment can greatly improve the coercivity of PrFeO 3 ceramic and thus change the magnetic properties from antiferromagnetic to ferromagnetic. The high correlation between the magnetization parameters and bonding characteristics indicated that signifificant contracting of the Fe3+ O c 2− bonds and decrease in Fe3+ O d 2− Fe3+ linkage angles were the main origins of the strong ferromagnetism in the PrFeO 3 ceramic. The PrFeO 3 sample prepared by sol–gel method has good reflection loss. When the simulated thickness is 2 mm, the reflection loss reaches −36.87 dB at 15.92 GHz. The preparation process of the sol–gel method is simple and can be used to synthesize single phase at low temperature, but it is only suitable for the synthesis and performance testing of single phase. The solid-state reation method can be used to determine the phase relationship and phase properties, but it requires high temperature and long annealing time. The experimental results show that the sol–gel method is more suitable for the study of material properties. These results demonstrate the potential application of PrFeO 3 ceramics in magnetic materials and microwave absorbing field. [ABSTRACT FROM AUTHOR]

Perovskite LaCoO 3 has unique mixed ionic electronic and structural defects, which has high research value in microwave absorption field. LaCoO 3 precursor was prepared by sol-gel method, and LaCo 1− x Fe x O 3 (Fe-LCO, x = 0, 0.05, 0.1 and 0.15) with rhombic symmetric structure was successfully synthesized at 600 °C. By refinement of X-ray diffraction (XRD) (Rietveld analysis), it was found that Fe doping makes LaCoO 3 lattice constant and cell volume increase. As a dielectric loss microwave absorbing material, the electromagnetic attenuation of LaCoO 3 is mainly due to the conduction loss, while the interface and dipole polarization are secondary reasons. It finds that Fe doping can improve the wave absorption performance of LaCoO 3. The best absorbing performance was obtained when Fe content is x = 0.1, with the maximum reflection loss of − 38.99 dB at 10.8 GHz and the effective absorption bandwidth (RL<−10 dB) is 4.48 GHz, while the corresponding thickness was only 3 mm. In summary, LaCoO 3 has broad application prospects in X and Ku bands. • The study focus on rare earth perovskite can expand and popularized of their application in the field of absorption. • LaCo 1- x Fe x O 3 composites have tunable Impedance matching performance and high-performance microwave absorption by ions doping. • The influence of dielectric loss and magnetic loss on material is analyzed in detail. • Composites can still maintain the effective bandwidth at 4–5 GHz when the reflection loss reached − 30 dB and above. • This work develops the application potential of LaCoO 3 in the field of absorption other than photocatalytic field. [ABSTRACT FROM AUTHOR]

• The Bi 1–x Ca x FeO 3 (x = 0.0, 0.05, 0.10, 0.15) nanopowders were prepared by sol–gel method. • Study its performance changes by analyzing the unit cell parameters, bond length, bond angle and valence. • The possible mechanism of improving magnetic properties and microwave absorption properties via calcium doping bismuth ferrite was analyzed. Bi 1- x Ca x FeO 3 (x = 0.0, 0.05, 0.1, 0.15) nanopowders were prepared using the sol–gel self-diffusion combustion technology. The effects of structure and grain size changes during the substitution of Bi ions by Ca ions on the magnetic properties and wave absorbing properties of BCFO are discussed. Single-phase BiFeO 3 is a typical rhombohedral R 3 c structure. When the doping amount reaches 0.15, the Ca2+ induced BCFO structure gradually changes to the Pm -3 m phase. The small-sized alkaline earth metal ions Ca2+ (0.99 Å) can successfully replace the A-site Bi3+ ions in BiFeO 3. Ca2+ doping improves the BFO spin helical modulation structure and change the Fe-O-Fe bond angle, thus enhancing the magnetic properties of BCFO. When the doping amount of Ca2+ is 0.10 and the simulated thickness is 2 mm, the best absorption performance at 10.23 GHz is −36.91 dB, and its effective bandwidth reaches 2.81 GHz, which has a good broadband effect. This study provides a reliable candidate material for the synthesis of electromagnetically attenuating ceramic materials with excellent properties. [ABSTRACT FROM AUTHOR]

Yttrium perovskite ferrite has a stable and symmetrical crystal structure and a simple preparation route. However, it exhibits poor absorption performance at 17–18 GHz. Several studies in the past have reported on the formation of mixed-valence states induced by the addition of monovalent K ions. In this study, YFeO 3 was synthesized by doping with monovalent K via the sol-gel auto combustion method. This greatly optimized the wave-absorbing properties and effective bandwidth of YFeO 3. The influence of different K additions on the absorption properties of the materials was also studied. All the hybrid composites showed excellent absorbing properties, with Y 0.8 K 0.2 FeO 3 having an effective bandwidth of 4.88 GHz at a simulated thickness of 2.0 mm, Furthermore, the reflection loss (RL) value of Y 0.7 K 0.3 FeO 3 reached − 30.56 dB at 15.44 GHz (effective bandwidth up to 4.72 GHz) corresponding to the thickness of only 1.6 mm. This demonstrates that this broadband effect is greater than other similar materials. Moreover, the as-prepared samples completely covered the X and Ku band at only 2.2 mm, and the maximum effective bandwidth reached 5.28 GHz at 2.0 mm. The excellent wave absorption and frequency broadening effects were due to the various loss mechanisms and improved impedance matching characteristics caused by doping. • The study focus on multiferroic properties can expand and popularized of their application in the field of absorption. • Y 1- x K x FeO 3 composites have tunable electromagnetic properties and excellent microwave absorption. • The influence of dielectric loss on dielectric material is analyzed in detail and the conduction loss is dominant. • Composites can still maintain the effective bandwidth at 4–5 GHz when the reflection loss reached − 30 dB and above. • This work develops the application potential of YFeO 3 in the field of absorption other than photocatalytic field. [ABSTRACT FROM AUTHOR]

• Pure phase barium ferrite was prepared by sol–gel method. • Nd doping improves the magnetic properties and microwave absorption properties of barium ferrite. • Study its performance changes by analyzing the unit cell parameters, bond length, bond angle and valence. Barium ferrite (BaFe 12 O 19) is a multiferroic material with many excellent properties and is easily available. It has good magnetic performance and microwave absorption performance, but it only has the maximum transmission loss in the high-frequency range. To improve its performance, the method of doping is used to improve. The Ba 1-x Nd x Fe 12 O 19 (0 ≤ x ≤ 0.15) was prepared by the sol–gel method. Through the XRD, SEM, VSM, and VNA to characterized the structure and performance of the samples. The results show that Nd ions replace Ba in barium ferrite, and no second phase appears. Along with the doping content increases, the particle size gradually decreases. There is the maximum saturation magnetization and coercive force when x = 0.10. It is attributed to the magnetic Nd ion replacing Ba2+, the magnetic moment increases cause the saturation magnetization increases, the change of Fe3+ and Fe2+ led to the magnetocrystalline anisotropy and the coercive force are increases. When x = 0.10, the complex permittivity increases, the microwave absorption characteristics become well which the maximum reflection loss reaches −34.4 dB, and the bandwidth increases to 4.69 GHz. It can be used in a wider range of fields. [ABSTRACT FROM AUTHOR]