M-type Barium Ferrite Research Articles

Preparation of M-type barium ferrite submicron absorbing powder by one-step high-temperature ball milling and its particle structure regulation

This study investigates a simple and rapid process for directly preparing M-type barium ferrite using high-temperature ball milling. By adjusting the rotation speed of the high-temperature ball milling, the morphology and size of the powder can be altered to regulate its electromagnetic properties, aiming for an overall good absorbing effect. The powder’s morphology, agglomeration properties, elemental valence states, and electromagnetic parameters were characterized using SEM, BET, XPS, EDS, and VNA. The results show that as the milling speed increases, the particle size of the M-type barium ferrite decreases, transitioning from the typical hexagonal flake particles to spherical block particles, forming a porous loose structure with richer dielectric loss mechanisms and enhanced electromagnetic wave loss capacity. Electromagnetic loss performance analysis indicates that at a milling speed of 50 rpm, the powder achieves the best electromagnetic loss of −61.16 dB at a matching thickness of 8.77 mm and a microwave absorption bandwidth of 4.1 GHz.

Structural, magnetic, optical, and electronic properties of vanadium-doped barium hexaferrite nanoparticles: Experimental and DFT approaches

Vanadium-doped barium hexaferrite with a nanostructure is a highly valuable material in various technological fields, such as electronics, permanent magnets, and sensors. The Ba1-xFe12-xVxO19 (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1) nanoparticles derived from the aqueous solutions containing Fe:Ba molar ratio of 10:1 through the sol-gel auto-combustion method. Computational study was also performed using the first-principles density functional theory (DFT) approach. Crystal structure optimization, band structure, and density of states (DOS) calculations were conducted by CASTEP code. The variation of the structural, magnetic, optical, morphological, and electronic properties of V5+-doped barium hexaferrite was investigated. The XRD analysis combined with the Rietveld refinement showed the hexagonal structure of M-type barium ferrite (BaM), confirmed by the FT-IR analysis. The morphology of BaM nanoparticles was studied by the FE-SEM and TEM micrographs. In addition, magnetic and optical properties were analyzed through VSM and UV–Vis analysis. Crystallite size was found to be highly effective in tuning the coercivity and optical band gap of barium hexaferrites, which varied, respectively, from 3.24 to 4.83 kOe, and 2.69–3.69 eV. Magnetic results showed that several variables like cations distribution, lattice strain, and hematite secondary phase affected the nanoparticles’ magnetization. The DFT simulation results showed a sharp reduction of electronic band gap energy whether V takes the position of Ba or Fe (from 1.10 eV in undoped to 0.64 and 0.14 eV in doped structures). The projected density of states (PDOS) calculations demonstrated that the d orbitals of V and Ba mainly contribute to the valence band maximum (VBM) and conduction band minimum (CBM), respectively.

Investigating Enhanced Microwave Absorption of CNTs@Nd0.15-BaM/PE Plate via Low-Temperature Sintering and High-Energy Ball Milling.

Composite plates comprising a blend of rare earth neodymium-(Nd) doped M-type barium ferrite (BaM) with CNTs (carbon nanotubes) and polyethylene WERE synthesized through a self-propagating reaction and hot-pressing treatment. The plates' microscopic characteristics were analyzed utilizing X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR), thermo-gravimetric analysis (TGA), Raman, and scanning electron microscopy (SEM) analytical techniques. Their microwave absorption performance within the frequency range of 8.2 to 18 GHz was assessed using a vector network analyzer. It showed that CNTs formed a conductive network on the surface of the Nd-BaM absorber, significantly enhancing absorption performance and widening the absorption bandwidth. Furthermore, dielectric polarization relaxation was investigated using the Debye theory, analyzing the Cole-Cole semicircle. It was observed that the sample exhibiting the best absorbing performance displayed the most semicircles, indicating that the dielectric polarization relaxation phenomenon can increase the dielectric relaxation loss of the sample. These findings provide valuable data support for the lightweight preparation of BaM-based absorbing materials.

Effect of Ce doping on electromagnetic characteristics and absorbing properties of M-type barium ferrite

In this study, Ce3+-doped M-type barium ferrite BaCexFe12-xO19 (x = 0 ∼ 1.2) was prepared by sol-gel method. The effects of Ce3+ doping on the crystal structure, microstructure, electromagnetic properties and absorption properties of M-type barium ferrites were investigated. The results indicate that the crystal structure remains unchanged with the increase of Ce3+ doping. The crystal size of Ce3+ doped barium ferrite is in the micro-meter range, and the grain size remains almost constant with increasing doping. The addition of Ce3+ to the BaFe12O19 samples resulted in significant improvements in their electromagnetic and microwave absorption properties. These improvements were mainly due to the synergistic effect of magnetic and dielectric losses. Among the samples doped with different concentrations of Ce3+, BaCe0.2Fe11.8O19 exhibited the best absorption performance, which has a minimum reflection loss of −58 dB and an effective absorption bandwidth of 9.44 GHz at a matched thickness of 2.3 mm. This study proposes an efficient electromagnetic wave absorber with a wider effective absorption bandwidth.

Investigation effect of Lu-substitution on structural, morphological, magnetic, and dielectric properties of BaM hexaferrite synthesized using a co-precipitation method

In this paper, we synthesized Lu-substituted M-type barium ferrites (BaLuxFe12-xO19, x = 0, 0.2, 0.4, 0.6, 0.8) by chemical co-precipitation using a non-stoichiometric ratio of raw materials. We investigated their structure, XPS, and EDX spectra, morphology, and magnetic and dielectric properties. The XRD patterns showed that the diffraction peaks shifted toward a lower angle and the lattice constant ratio (c/a) was less than 3.98, which was within the allowable range of magneto-plumbite structure. XPS and EDX spectra confirmed the presence of O, Fe, Ba, and Lu elements in the samples. SEM images revealed that the ceramic samples sintered at 1330 °C had a regular and obvious hexagonal structure. Lu substitution promoted grain growth, with an average grain size increase of 163% and a maximum grain size of 21.77 µm. Hysteresis loops indicated the formation of a multi-domain structure in the samples. The coercivity decreased from 2035.82 Oe to 574.84 Oe and the saturation magnetization decreased as well but still exceeded 58 emu/g. The dielectric constants of all the samples were in the order of 103 to 104 and the substitution of Lu significantly increased it to about 16k. The tangent loss could be maintained below 0.5, with a minimum of approximately 0.1. The Lu-substitution barium ferrites with high saturation magnetization, low coercivity, high dielectric constant, and low tangent loss coexistence may be a potential candidate for application in low-frequency wireless communication with miniaturization and multifunction.

Structure and magnetic properties of M-type barium ferrite co-doped with Sm and Nb prepared by solid-phase sintering

M-type barium ferrite with the formula Ba1−xSmxFe12−yNbyO19 (x = 0.00–0.10, y = 0.00–0.20), which was co-doped with Sm3+ and Nb5+ ions, was synthesized experimentally by a modified solid-phase reaction method. The crystal structure of samples was determined by X-ray diffraction, which confirmed that they were of high purity. The X-ray diffraction data were fitted with a full-spectrum correction using GSAS software. By Fourier transform infrared spectroscopy, the samples were observed to exhibit bands due to tetrahedral and octahedral sites at 598 cm−1 and 445 cm−1, respectively. The samples were examined by field emission scanning electron microscopy, which showed that they partly comprised hexagonal structures but mostly consisted of irregular structures with rounded edges. Characterization of the elemental contents of the samples by energy-dispersive spectroscopy revealed an increase in the contents of Sm and Nb and a decrease in the contents of Ba and Fe. The magnetic properties of the samples were examined using a vibrating sample magnetometer. The results showed that the saturation magnetization and residual magnetization of the samples decreased slightly with an increase in the contents of the dopants. The coercivity reached its maximum value, namely, 3367.53 Oe, when x = 0.04 and y = 0.08.

Investigation of crystal structure, Raman spectroscopy and magnetic properties of La-Zn substituted oriented M-type hexagonal barium ferrites

M-type hexagonal barium ferrite (BaM) has received much attention in the application of self-biased microwave devices because of its large anisotropic field (Ha) and high saturation magnetization (Ms), but the increased Ha inevitably increases the microwave magnetic loss of the device. In addition, the devices need to have a high Ms for high frequency applications. To address these issues, we used La3+ and Zn2+ instead of Ba2+ and Fe3+ ions to modulate the Ha and Ms of BaM, respectively. Ba1-yLayFe12-xZnxO19 (x=y=0.1–0.5) M-type hexagonal ferrite was synthesised by conventional solid-phase methods. The La-Zn co-substituted BaM samples were shown to be purely single phase by X-ray diffraction (XRD) analysis. The lattice parameters, specific surface area, crystallite size, dislocation density and microstrain of the samples were also calculated using the XRD data. Furthermore, La3+ and Zn2+ can not only modulate the sample Ha and Ms between 10,214–12,102 Oe and 62.94–78.23 emu/g, respectively, while making the sample more denser. At x=0.3 BaM detects relatively satisfactory properties: large Ms=63.12 emu/g, suitable Ha=10,214 Oe and Hc=2248.87 Oe, high Mr/Ms=0.832 and narrow ferromagnetic resonance linewidth (= 903 Oe), which provide good candidates for next-generation self-biased and low-loss microwave wave devices.

Magnetic properties of Sm-doped M-type barium ferrite by high-energy ball mill-assisted solid-phase reaction method

The primary objective of this study is to enhance the overall magnetic properties of pure barium ferrite through the addition of trace amounts of the light rare earth element Sm. This approach is more cost-effective compared to using heavy rare earth elements. The M-shaped barium ferrite, denoted as Ba1−xSmxFe12O19, was synthesized using a combination of solid-phase sintering method and high-energy ball milling. The high purity of samples was confirmed by determining their crystal structure using XRD. The internal structure of samples was examined using FTIR, and it was observed that the samples contained tetrahedral and octahedral clusters with corresponding bands at 599 cm−1 and 445 cm−1, respectively. The appearance of samples was examined using FESEM, and it was found that grains had hexagonal structures. EDS was used to characterize the elemental content of samples, and it was found that the content of Ba decreased with an increase in the content of Sm. The magnetic properties of samples were examined using VSM, and the coercivity reached a maximum value of 3096.22 Oe at a dopant fraction of 0.06, and the saturation magnetization reached a maximum value of 73.115 emu/g. The synthesized material has the potential for utilization in magnetic recording applications.

Application of Steinmetz Formula in M-Type Barium Ferrite

Application of Steinmetz Formula in M-Type Barium Ferrite

Accurate measurements of the ferromagnetic resonance linewidth of single crystal BaM hexaferrite spheres employing magnetic plasmon resonance theory

Accurate measurements of the intrinsic ferromagnetic linewidth of a single-crystal Sc-doped hexagonal M-type barium ferrite (BaM) 308-µm-diameter sphere at millimeter-wave frequencies employing a subwavelength cavity are described. The magnetic hysteresis of the resonance frequency and Q-factor of the dominant resonance (which has a plasmonic character) in a hexaferrite sphere are reported. Measurements performed in a fixture open to free space also show that the ferromagnetic linewidth significantly increases as compared to measurements in a closed cavity. This effect can be attributed to radiation losses, as revealed by an electrodynamic magnetic plasmon resonance model, and is relevant for measurements in open structures, such as microstrip lines or coplanar waveguides. The impact of finite resistivity on the linewidth was also analyzed.

The Ordered Mesoporous Barium Ferrite Compounded with Nitrogen-Doped Reduced Graphene Oxide for Microwave Absorption Materials.

Nanocomposites with hierarchical pore structure hold great potentials for applications in the field of microwave-absorbing materials because of their lightweight and high-efficiency absorption properties. Herein, M-type barium ferrite (BaM) with ordered mesoporous structure (M-BaM) is prepared via a sol-gel process enhanced by mixed anionic and cationic surfactants. The surface area of M-BaM is enhanced almost ten times compared with BaM together with 40% reflection loss enhancing. Then M-BaM compounded with nitrogen-doped reduced graphene oxide (MBG) is synthesized via hydrothermal reaction in which the reduction and nitrogen doping of graphene oxide (GO) in situ occur simultaneously. Interestingly, the mesoporous structure is able to provide opportunity for reductant toenter the bulk M-BaM reducing its Fe3+ to Fe2+ and further forms Fe3 O4 . It requires an optimal balance among the remained mesopores in MBG, formed Fe3 O4 , and CN in nitrogen-doped graphene (N-RGO) for optimizing impedance matching and greatly increasing multiple reflections/interfacial polarization. MBG-2 (GO:M-BaM = 1:10) achieves the minimum reflection loss of -62.6dB with an effective bandwidth of 4.2GHz at an ultra-thin thickness of 1.4mm. In addition, the marriage of mesoporous structure of M-BaM and light mass of graphene reduces the density of MBG.

Design, fabrication, and magnetic properties of novel (Ni,Cr,Zr)-co-doped M-type barium ferrite ceramics

Multicomponent co-doping is an effective method to balance the counteracting magnetic properties of ferrite ceramics. In this work, novel (Ni,Cr,Zr)-co-doped M-type barium hexaferrites (BaFe12-3xNixCrxZrxO19, x = 0–0.8) were designed and synthesized by traditional solid-state reaction. Thermogravimetric analysis indicated that NiO would participate in the formation of secondary phase NiFe2O4 in the as-synthesized powder. Through traditional solid-state sintering, by using the synthesized pure-phase magnetic powders, almost full-dense ceramics were fabricated. Visual high-temperature deformation analysis revealed that there was no obvious difference in the sintering behavior and densification temperature of the ceramics with different compositional x, due to the low sintering activity of the as-synthesized magnetic powders. And X-ray diffraction analysis indicated that all the fabricated ceramics are of pure-phase M-type barium ferrite, and the lattice parameter c/a firstly increased as x raised up to 0.4 and then remained almost unchanged with further increased x, even if the lattice distortion became heavier. Microstructure examination revealed that the grain size monotonously decreased as the quantity of the substituent ions increased. The remnant magnetization and coercivity of the fabricated ceramics decreased monotonously as x increased, while the saturated magnetization could be maintained till the samples with x ≤ 0.4. Taking all the parameters into consideration, the samples with x = 0.4 might be a good candidate for transformer cores.

Effect of sintering temperature on microstructure and magnetic and dielectric properties of M-type barium ferrites

In this study, the effect of sintering temperature on microstructure, magnetic properties and dielectric behavior of M-type barium ferrites (BaM) is systematically analyzed. BaBi0.45(CoTi)1.2Fe9.15O19 samples with a dense microstructure and typical hexagonal shape are obtained at the sintering temperature of 920 °C. Moreover, the permittivity (ε′) of BaM increases to 21.41 at 0.01 GHz and the permeability (μ′) increases to 10.82 at the optimized temperature of 920 °C. Based on mathematical fitting, the saturation magnetization (4πMs) of samples is calculated to be 3272.27 Gauss and the magnetocrystalline anisotropy constant K1 is found to be 4.18 × 106 erg cm−3. More interestingly, the magnetic loss angle tangent (tanδμ) is reduced to 2.7 × 10−1 and the dielectric loss angle tangent (tanδε) is reduced to 5.8 × 10−3. The optimized magnetic and dielectric properties, with low losses, enhance the suitability of BaM ferrites for miniaturized microstrip devices.

Synthesis of low-temperature sintered M-type barium ferrites with enhanced microstructure, magnetic and dielectric properties

M-type barium ferrites (BaM) are utilized in the preparation of ferrite circulators due to their excellent magnetic properties. However, high sintering temperature of BaM is one of the major problems unsuitable for actual production requirements. In this study, Bi3+ ions from the low-melting point oxide bismuth(III) oxide (Bi2O3) were made to substitute Fe3+ ions to reduce the sintering temperature and control the magnetic properties. Addition of an appropriate content of Bi3+ ions at the sintering temperature of 900 °C led to the disappearance of the second phase, and a pure BaBix(CoTi)1.2Fe9.6−xO19 phase was formed. The results exhibited the existence of dense microstructure in BaM ceramics. Moreover, when the x value of Bi2O3 was 0.45, the permeability of the sample increased from 12.59 to 21.6 at 10 MHz, the saturation magnetization reached 3313.34 gauss, and the permittivity increased from 10.75 to 21.24. Permeability and permittivity were found to be approximately equal. Interestingly, addition of excessive Bi2O3 led to the formation of the second phase, and the microstructure exhibited the appearance of abnormal grains. However, BaM still maintained acceptable magnetic properties. The results showed that the addition of Bi3+ ions could reduce the sintering temperature of the ferrite and simultaneously adjust the magnetic and dielectric properties. Therefore, this material may have good performance in the preparation of ferrite circulators.

Growth of Y3Fe5O12-BaFe12O19 nanocomposite film with high remanence ratio for its exchange spring coupling behavior

Preparation of a high remanence ratio of M-type barium ferrite film is highly desirable in self-biased microwave devices. In this letter, Y3Fe5O12-BaFe12O19 nanocomposite film with a high remanence ratio was deposited on the Al2O3 substrate. Multiple crystal structure characterizations confirm that the Y3Fe5O12 film was grown on the orientation BaFe12O19 film surface with high crystallinity and low roughness. The magnetism measurement displays that the nanocomposite film has a high remanence ratio of 0.65 for its high exchange spring coupling. Consequently, this work gives an approach to preparing ferrite film with a high remanence ratio which is applied in self-biased devices.

High microwave absorption performance in Nd-substituted BaM/GO through sol-gel and high energy ball milling process

In this paper, a series of compound materials with different proportions of rare earth neodymium (Nd) doped M-type barium ferrite (BaM) and the mixture Nd-BaM with graphene oxide (GO) are prepared through the sol-gel method and high-energy ball milling route. The surface morphology, composition and electromagnetic properties of those materials are analyzed through XRD, SEM, TG, Raman and the vector network analyzer. It is found that the Nd-BaM particle is adhered on the surface of GO with the nanometer size. The electromagnetic performance can be severely affected by the doping amounts of Nd and the blending amounts of GO. Moreover, the microwave absorption performance of the compounds is studied in the frequency range of 2–18 GHz. For Nd0.15-BaM/3%GO, the minimum reflection loss is − 82.07 dB at 12.65 GHz and the scope of the effective absorption band is 6.08 GHz with a thickness of 2 mm. Because of its good impedance matching, the interface polarization and electron polarization between Nd-BaM and GO, the electromagnetic wave occurs multiple reflection in this material. Compared with pure BaM or BaM/GO, the Nd substituted BaM/GO has excellent microwave absorption performance, which has a certain prospect in the microwave absorbing field.

Microstructure, magnetic, and dielectric properties of Co–Zr co-doped hexagonal barium ferrites based on the sintering temperature and doping concentration

In this work, M-type hexagonal barium ferrites co-doped with Co and Zr atoms were prepared by a solid-phase method based on the sintering temperature and doping concentration. First, the influences of the sintering temperature on the crystal structure, microstructure, and magnetic properties of ferrites were studied. The crystallinity of the materials increases with the sintering temperature and obtaining high density and uniform grain size at 1300 °C, which promotes grain-boundary diffusion and suppresses grain-boundary migration. Second, the dependence of the crystal structure, microstructure, magnetic, and dielectric properties of Ba(CoxZrx)Fe12−2xO19 on the doping concentration (x = 0, 0.2, 0.4, 0.6) was investigated at sintering temperature of 1300 °C. The increase of the crystal parameter c with x value reveals that the ions of Co2+ and Zr4+ successfully replace the Fe3+ ions. Additionally, the co-doping ions of Co2+–Zr4+ promote the grain-boundary migration and result in some large size grain (> 20 mm) that appeared and increased with the doping concentration. The magnetic hysteresis loops reveal the saturation magnetization increases from 60.45 to 68.6 emu/g, and the coercivity decreases from 1800 to 190 Oe with the x increased to 0.6. The dielectric properties measurement displays the Co–Zr co-doping can improve the dielectric and reduce the dielectric loss. The highest value of the real part of permittivity (e′) and the lowest value of the imaginary part of permittivity (e″) can be obtained at a doping concentration of x = 0.4.

Effect of calcination temperature on structural and terahertz characterization of M-type barium ferrite

We present detailed studies on M-type barium ferrite (BaFe12O19, BaM) synthesized by the sol–gel combustion method that is calcined at 1000 °C, 1100 °C, and 1200 °C. In addition to the structural properties, we present the THz optical dielectric constant and conductivity response of this system as a function of calcination temperature. From x-ray diffraction (XRD) studies, a single-phase of the hexagonal structure is established, and the crystallite size (Dhkl) was calculated to be in the range of 26 nm–28.54 nm. The XRD patterns were analyzed to evaluate lattice parameters (a, c, V) and x-ray density (ρx). Home built terahertz time-domain spectroscopy was performed to investigate the complex refractive index (n̂s) of the samples at room temperature in a frequency range of 0.2 THz–1.2 THz. The complex dielectric constant (ε̂s) and conductivity (σ̂s) as a function of calcination temperature were deduced using THz spectroscopy data. The complex dielectric constant and conductivity of BaM were determined for the calcination temperatures of 1000 °C, 1100 °C, and 1200 °C.

Synthesis of broad microwave absorption bandwidth Zr4+-Ni2+ ions gradient-substituted barium ferrite

In this study, to effectively broaden the absorption bandwidth of M-type barium ferrite (BaM) in frequency range 2–18 GHz, Zr4+-Ni2+ ions gradient-substituted BaM samples were synthesized via secondary heating the mixtures of homogeneous-substituted Ba(ZrNi)0.6Fe10.8O19 and Ba(ZrNi)0.7Fe10.6O19. Effects of primary and secondary heat treatment on electromagnetic (EM) parameters of gradient-substituted BaM were investigated in detail. Permittivity values of samples are mainly controlled by primary heat treatment, enhancing with increasing temperature, whereas magnetic loss range is enlarged by improving primary and secondary heat treatment. As a result, the frequency range with μ" value > 0.3 reaches to 6.84 GHz for the sample “1400–1200 °C”. Enhanced dielectric and magnetic losses contribute high attenuation constant over wide frequency range, finally resulting in broad absorption bandwidth of 6.24 GHz at matching thickness of 2.8 mm. The bandwidth improved by 21% and 44% compared to that of original Ba(ZrNi)0.6Fe10.8O19 and Ba(ZrNi)0.7Fe10.6O19, respectively. This study sheds new light on the preparation of broadband absorbing materials.

A preliminary study of oxides of Fe doped with Ba, Co, Cu and synthetized by the citrate sol–gel combustion route

In the present work we report the synthesis of mixed ferrites doped with Co2+, Cu2+ and Ba2+ cations, using citrate sol–gel combustion route in air atmosphere, at 950 °C for 3 hours, produced substituted M-type barium ferrites powders particles with crystallite sizes varying between 145 and 155 nm. The percentages of yield obtained were on average 42%. The synthesized ferrites were characterized by techniques such as powder X-ray diffraction, evidencing the formation of M-type barium hexaferrite and copper and cobalt substituted M-type barium ferrite with hematite in smaller proportion. The possible growth of M-type barium ferrite with copper and cobalt may be due to a larger size of the cobalt atom with respect to copper and that a higher proportion of cobalt salt was used in the synthesis route. Increase in the metal ion substituted content leads to a decrease in the lattice strain and may be responsible for an increase in the crystallite size because greater tensile strain leads to elongation of the particles. The particle size of the synthesized ferrites differs significantly when they are doped, with Ferrite doped with copper having the smallest particle size compared to Ferrite doped with cobalt. We also performed spectroscopic analyses, RAMAN that showed, the substitution of cooper or cobalt in the M-type barium ferrite powders particle leads to a minor intensity of resonance band when compared with the parent compound and the differences between Fe3+, Cu2+ and Co2+ ions in a tetrahedral coordination is their ionic radii. The increase in the ionic radii causes a local distortion and vibrational bands of distorted polyhedra in substituted M-type barium ferrites. The chemical composition of this sample was determined as Ba1.0Fe11.83O19.22, Ba1.0Co1.02Fe11.01O18.35 and Ba1.02Cu0.56Fe11.35O18.26 using an AAS device. Both are very close to the theoretical formula. The influence of the synthesized ferrite samples was explored in the ozonation of a dye of unknown chemical structure. The effect was evidenced by visible ultraviolet spectroscopy technique. The results obtained show that the ink could be decolorized by applying oxidation by ozonation, however, when substituted M-type barium ferrite is added, the discoloration increases when this is doped with copper and cobalt, being higher using this last ferrite. The degradation process by ozonation presented in this work, carried out in the presence of copper and cobalt substituted M-type barium ferrites, would constitute an example of technology for the environment.