Search

Due to the excessive use of electronic devices in this modern technological age, the issue of electromagnetic interference (EMI) has become a concern. To address this, Ca–Pb W-type hexaferrites were synthesized with the composition Ca0.5Pb0.5Co2−xMgxLayFe16−yO27, where x and y vary between 0.0 and 1.0, with a step of 0.2 and 0.02, respectively. The samples were prepared using the sol–gel auto-combustion method. The results of the X-ray diffraction analysis showed the formation of a single-phase hexaferrite structure by examining its structural parameters. This was confirmed as all the peaks observed matched the reference pattern stored in the ICDD database with the number 01-082-0041. Scherrer's formula was used to calculate crystallites size which ranged from 41 to 76 nm. The formation of hexaferrites was confirmed using Fourier transform infrared spectroscopy, which detected two absorption bands below 1000 cm−1. Energy-dispersive X-ray spectroscopy revealed that all of the sample's elements were present. Scanning electron microscopy micrographs revealed the shape and distribution of the particles. Frequency-dependent dielectric parameters were evaluated for all concentrations in a range between 1.0 MHz and 3 GHz. At frequencies that are relatively low, the materials exhibit high values of both dielectric constant and dielectric loss. Furthermore, the AC conductivity of these materials is significantly low at lower frequencies. However, as the frequency increases, the conductivity of the materials gradually begins to increase, and this rise is marked by the emergence of resonance peaks. These characteristics make the material well-suited for use as electromagnetic interference (EMI) filters and chokes. [ABSTRACT FROM AUTHOR]

The structural, magnetic, and dielectric properties of Yb ions substituted Ca-hexaferrites (Ca-HFs) synthesized using the citrate sol–gel method were studied. XRD and SEM, techniques were used to evaluate the size and shape of the samples. X-ray powder diffraction (XRD) patterns of prepared samples revealed the production of a single M-type single phase hexagonal ferrite with space group 167: R-3c, hexagonal of P63/mmc for structural characterization. Using a scanning electron microscope, the surface morphology of the particle was investigated, and the particle size was determined (SEM). FTIR spectra confirmed the iron–oxygen bands of X-type hexagonal ferrites at tetrahedral and octahedral sites. The high influence of Yb+3 substitutions on the FTIR spectra further confirmed that the dopants play a significant role in these ferrites. The electrical and dielectric properties of Yb substituted Ca-HFs were investigated using the complex impedance spectroscopy technique at various temperatures, frequencies, and substitution ratios. Yb substitution was discovered to have a significant impact on dielectric loss, dielectric constant, Ac conductivity, and dissipation factor. It was fascinating to see how Ytterbium replacement resulted in a significant improvement in magnetic characteristics. With a given substitution ratio, activation energy levels can be altered to a certain level. The Verway Hopping Model, Maxwell Wagner Model, and Koop's theory were used to describe the conduction and polarization mechanisms. The trend was also influenced by the substitution of Yb. Eddy current losses, devices like Multi-Layer Chip Inductors (MLCI), and other microwave applications can benefit from the achieved ranges of both features. [ABSTRACT FROM AUTHOR]

The rare earth (Yb3+) substituted W-type hexagonal ferrites with composition CaPb 2-x Yb x Fe 16 O 27 (x = 0.0, 0.5, 1.0, 1.5, 2.0) were synthesized by a facile and cost-effective sol-gel auto combustion method with post heat treatment. The synthesized hexagonal ferrites were characterized by a variety of analytical techniques, and an impedance analyzer was used to investigate the effects of Ytterbium on structural, magnetic, spectral and dielectric properties. The relationship between their impedance, structure and dielectric properties was investigated. The X-ray diffraction patterns verify the presence of single-phase W-type hexagonal ferrites. Physical properties such as D bulk (bulk density), D xrd (X-ray density), and P (porosity) of the CaPb 2-x Yb x Fe 16 O 27 W-type hexagonal ferrites were calculated. The bulk density of all the samples was decreased, and X-ray intensity was increased with the Ytterbium replacement in the W-type hexaferrite. By adding Yb3+ ions, the lattice parameters, cell volume and X-ray density were reduced due to the substitution of ytterbium with smaller ionic radii compared to the lead ion with large ionic radii. The AC-conductivity was increased from (1.523 × 10−5 to 6.699 × 10−5) Ωcm−1. The dielectric constant and tangent loss was found to decrease substantially. The magnetic properties were found to enhance by the substitution of Yb3+. The low coercivity value of Yb3+ substituted W-type hexagonal ferrites are suitable for magnetic recording media operated at a high-frequency regime. The enhancement of electrical, dielectric and magnetic characteristics suggests these materials as promising for multi-layer chip inductors (MLCIs) circuit applications. [ABSTRACT FROM AUTHOR]

M -type hexagonal ferrites with compositions Ca 1 − x CrxFe 1 2 O 1 9 at (x = 0. 1 , 0.2, 0.3, 0.4, 0.5) were successfully prepared by sol–gel auto combustion method and then immersed with polyvinyl alcohol (PVA) by ultrasound-assisted in situ emulsion technique. The results indicate that the synthesized nanoparticles were diffused homogeneously in PVA retaining the size and shape of the particle. The single-phase M -type hexagonal structure was revealed by X-ray diffraction (XRD) with extra 101 peak of PVA at 2 θ = 1 8 ∘ . The suitable signal-to-noise ratio in the high density recording media can be achieved due to the small particle size of the prepared composites as compared to pure hexaferrites. The interaction between PVA and nanoparticles was confirmed by Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) images revealed the homogeneous distribution of grains, the crystallite size was measured from SEM (25–38 nm), and it is also in agreement as calculated from the Scherer formula. Dielectric properties were also explored in the range of 1 MHz–3 GHz frequencies. Dielectric constant and dielectric loss were found to decrease with increasing frequency and decrease with the addition of ferrite ratio in the polymer matrix. This impact is because of the grain boundary at low frequency regime. The occurrence of resonance at high frequency regime recommends the investigated samples for multilayer chip inductor. The formation of PVA-Ferrite Nanocomposites was confirmed by the FTIR in the range of 3500–400 cm–1 wavenumbers. The FTIR spectra of ferrite-polymer composites (PF3,PF5) were shown. The absorption bands in the range of 500–600 cm–1 wavenumbers are due to stretching vibrations at tetrahedral sites and absorption bands in the 400–500 cm–1 wavenumbers demonstrate the octahedral site formation in the M-type hexagonal ferrites structure. The absorption band at 1600 cm–1 is due to the stretching bands of hydroxyl group -O-H. Slight shifts in the bands were recorded due to the addition of polymer. Due to the interaction of ferrites-polymer, force constant and electron density were found to be decreased. [ABSTRACT FROM AUTHOR]

In this work, sol-gel auto-combustion technique was employed to synthesize Pb2Co2-xNixFe28O46(x = 0.0, 0.4, 0.8, 1.2, 1.6, and 2) X-type hexagonal ferrites. Annealing of the samples was done at 1050 °C for 10 h. Formation of the X-type hexaferrites phase was confirmed by the XRD technique. Scanning electron microscopy was used to observe the morphology of the prepared samples. Crystallite size ranges from 15.40 to 10.10 nm. The unit cell volume was measured in the range of (2497.5-2514.1) Å . The cell volume and the lattice constants changed due to the difference in radii of the base and doping element. Distortion parameter (g) and dislocation density (δ) varied directly to site vacancies in the layers and the reordering of the lattice atoms during the transformation process. FTIR spectrum revealed the presence of particular absorption bands (metal-oxygen stretching vibration) which also confirmed the formation of hexagonal ferrites, and it was recorded in the range 600-4000 cm - 1 . Dielectric parameters exhibit frequency-dependent behavior. The dielectric constant (ɛ′), dielectric loss (ɛ″), and tan loss (tanδ) decreased abruptly at low frequency and then remained invariant up to 1.5 MHz. The higher values of the dielectric parameters recommend fabricated material a potential candidate for high-frequency applications. Dielectric constant and Q-value were found to increase with the increase in Ni content. All the samples revealed resonance peaks above 1.9 GHz which indicates the potential use of the material for EMI attenuation. The optimized dielectric nature of the prepared hexaferrites suggests the material to be useful in the manufacturing of multilayer chip inductors (MLCIs). [ABSTRACT FROM AUTHOR]

Hexaferrites of Sr1-xCrxFe12O19 with x = (0.0, 0.1, 0.2, 0.3, 0.4, 0.5) were fabricated by citrate sol–gel technique. Characterization of grown samples such as structural and morphological analysis was performed by XRD and Scanning Electron Microscopy (SEM). Effect of Cr3+ incorporation on the electrical, structural and dielectric properties of Sr1-xCrxFe12O19x = (0.0, 0.1, 0.2, 0.3, 0.4, 0.5) was reported. Confirmation of single phase M-type hexaferrite structure was carried out by the x-ray diffraction analysis. Lattice parameters have been reported to boost as the content of Cr3+ rises, which is due to the ionic size of the cation involved. SEM analysis indicates the decrease in grain size with the substitution of Cr3+. The dielectric constant and ac conductivity represent increasing behavior, while dielectric and tan loss indicate decreasing behavior with the increase in frequency and with Cr3+ content. The increasing decreasing trend of saturation magnetization was observed, and it is due to the different site occupancy of iron at different crystallographic sites. The coercivity values (6.64-6.72 KOe) of all samples were found to be in the range of M-type hexaferrites. These dielectric parameters values are appropriate for different applications in high-frequency devices such as modulators, phase shifters and also in longitudinal recording media. [ABSTRACT FROM AUTHOR]

The rapid industrialization of the world is critically influencing our environment and natural ecosystem. The researchers are taking keen interest to invent novel material as photocatalyst for non-degradable organic pollutants. Herein, we have fabricated Sm and Co substituted M-type hexaferrite with composition Ca0.5Pb0.5–xSmxCoyFe12–yO19, (x = 0.00–0.1; y = 0.00–1.00) by sol–gel auto-combustion approach. The effect of Sm2+ and Co3+ substitution in calcium-lead hexaferrite has been investigated for structural, morphological, dielectric and photocatalytic applications for organic pollutants. X-ray diffraction study exhibited the presence of the single-phase M-type hexaferrite with size ranged between 19–23 nm. The particle size, shape and elemental composition were determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis. It was investigated that the electrical resistivity was decreased, and drifts mobility increased with increasing Sm2+ and Co3+ contents in the doped materials. An inverse relation has been established between the dielectric constant and the dielectric loss up to a frequency of 9.0 GHz and remains constant above this frequency range. The synthesized materials may prove a suitable contender in the domain of high-frequency devices like circulators, filters, transformers and antennas and environmental remediation. The energy bandgap (Eg) was calculated from UV-visible absorbance spectra by Tauc plot. It showed decreasing trend from 2.2 to 1.95 eV for precursor and doped material (Ca0.5Pb0.5–xSmxCoyFe12–yO19, x = 0.1; y = 1.00) respectively. Narrowing of bandgap is considered an important factor for the degradation of industrial effluents. The doped materials have also been explored to study the photocatalytic efficiency using a batch reactor to remove methylene blue dye from the textile synthetic wastewater in the presence of visible light radiations at 668 nm, recording 87.50% of degradation efficiency. [ABSTRACT FROM AUTHOR]

M-type hexaferrites with composition Ca1−xCrxFe12O19 were synthesized by the sol–gel auto-combustion method. Structural, morphological and dielectric properties were explored. Annealing of the samples was done at 1200 °C for 8 h. XRD pattern reveals single-phase magnetoplumbite structure. The structural properties as lattice parameters, crystallite size and cell volume of Ca1−xCrxFe12O19 hexaferrites were evaluated. Crystallite size of the particle varied from 45.85 to 42.96 nm. Morphology of the samples observed by scanning electron microscopy reveals regular platelet hexagonal structure and all the grains were distributed homogeneously. Dielectric parameters such as dielectric loss, dielectric constant, tangent loss, electric modulus, ac conductivity and Q values of the prepared samples were also discussed. These measured dielectric parameters are appropriate for high-frequency applications such as microwave absorber, phase shifter, dielectric resonator and stealth technology. [ABSTRACT FROM AUTHOR]

The sol-gel auto-combustion method was employed to synthesize Ca 1-x Bi x Fe 12-x Co x O 19 M-type hexaferrites. X-ray diffraction (XRD) analysis confirmed the formation of a single phase M-type hexagonal structure, with a crystallite size ranging from 23.51 to 23.08 nm. The doping contents were found to decrease the bulk and X-ray densities while increasing the porosity. Fourier-transform infrared (FTIR) spectra showed the formation of metal-oxygen stretching vibrations that confirmed the hexagonal ferrites. The scanning electron microscopy (SEM) images revealed a regular platelet hexagonal structure with homogeneously distributed grains. The dielectric constant was high at low frequency and decreased with increasing frequency, while the dielectric loss decreased appreciably with doping. The saturation magnetization ranged from 38.27 to 15.51 emu/g, coercivity increased from 207.93 to 1359.69 Oe, and the squareness ratio was in the range of 0.19–0.78. All synthesized samples exhibited greater coercivity values than Mr/2, indicating their hard nature and potential use in high frequency applications. • Investigation of Bi-Co doping effect on multiple properties of M-type Calcium Hexaferrites. • Sol-gel auto-combustion technique used for sample preparation. • X-ray diffraction analysis confirmed pure crystalline phase with no impurity • SEM imaging showed the surface morphology of the synthesized hexaferrites • The dielectric constant was high at low frequency and decreased with the with doping. [ABSTRACT FROM AUTHOR]

The sol–gel technique was used to synthesize a series of six samples with nominal composition Sr2Co2Fe12 − 2xMnxPrxO22 (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.1). The XRD analysis revealed a well-defined Y-type hexagonal single phase structure. The characteristics such as crystal size, porosity, bulk density, aspect ratio and X-ray density were also calculated by XRD patterns. The crystal size has a range from 59.6 to 25.5 nm. The lattice constant 'a' varies from 5.89 Å to 5.96 Å and lattice constant c varies from 43.35 Å to 43.44 Å. The surface morphology was performed by SEM analysis of investigated sample. The DC resistivity was calculated and found in the range of 2.86 × 107(Ω cm) to 7.47 × 107(Ω cm). Both dielectric constant, dielectric loss decreased with applied frequency. The variation of values of dielectric constant and dielectric loss was explained with the help of Maxwell Wagner and Koops phenomenological theory. The magnetic properties such as saturation magnetization, retentivity, coercivity of investigated samples was performed through VSM. Due to high resistivity and low dielectric constant these materials are considered best for high frequency microwaves devices. [ABSTRACT FROM AUTHOR]