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The impact of Tb-Cr substitution in cobalt-based ferrites having composition Co1-xTbxFe2-yCryO4 (x=0.0-0.1, y=0.0-0.5) prepared by solid state reaction method on structural, magnetic and dielectric parameters was explored. Structural analysis was carried out by X-ray diffraction technique. A variation in lattice parameter (a) was observed as a func...
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... parameters were examined for a frequency range 1MHz to 3GHz using the two probe method. Figure 1 shows the thermogravimetric (TGA), differential gravimetric (DTA), and differential scanning calorimetric (DSC) studies for un-annealed Co0.96Tb0.04Fe1.8Cr0.2O4 ferrite sample. ...
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... differential scanning calorimetry (DSC) curve of the sample is also shown in Figure 1. In the DTA curve, peaks appeared at 65.31 °C, and 215.5 °C designate the breakdown of anions, whereas a sharp peak at 356 °C depicts the breakdown of metallic complexes. ...
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... from 3.68 to 3.93 g/cm 3 with the increase of dopants content, and it might be because the Tb ion has a higher atomic weight than the Co cation. The porosity varies from 24.6 to 22.8 %. Similar results were reported in the literature for rare earth substituted cobalt spinel ferrites (Dascalu, Popescu, Feder, & Caltun, 2013;Tahar et al., 2008). -xTbxFe2-yCryO4 (x = 0.0-0.1, y=0.0 ...
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... magnetization decreases, resulting in the Ms decreases for all Tb-Cr co-doped ferrites (L. Kumar & Kar, 2012). The remanence reduces from 13.38 to 8.12 emu/g by increasing the contents of dopants. The fitted curves of Ms, acquired from the law of approach to saturation, are calculated at 300 K for all samples and are shown in figures 4a to 4f. (x = 0.0-0.1, y=0.0-0.5) ...
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... grain size declines for higher dopants concentration and hence grain boundaries become larger, AC conductivity declines. -xTbxFe2-yCryO4 (x=0.0-0.1, y=0.0-0. ...
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... nature of real (M') and imaginary (M'') parts of electric modulus as a function of applied field frequency is significant to knowing the relaxation mechanism (Asif Iqbal et al., 2014). Figure 9 and figure 10 indicate the real (M') and imaginary (M'') parts of the dielectric modulus as a function of applied frequency. M'' increases with the rise in the biasing oscillating applied electric field and reaches the highest value at some applied frequency called relaxation frequency. ...
Citations
... Hexagonal ferrites have seven types, i.e., M, W, X, Y, Z, U, and R. Ztype hexagonal ferrites are more stable at high frequencies (GHz), which makes them valuable material for MLCIs, LC filers, transmitters, and microwave absorbers [11,12]. Z hexaferrites offer low coercivity, applicable as microwave absorbers for human protection in EM-polluted environments, military defense from enemy radar, and aircraft coating [2]. ...
Recently, hexagonal ferrites with extraordinary properties (dielectric, structural, and low reflection losses) have been used for microwave absorption and to resolve the EM (Electromagnetic) pollution issues. In the recent work, nano-sized Z-type hexagonal ferrites with chemical composition Ba3Co2InxFe24-xO41; 0.0 ≤ x ≤ 0.12 (in a single step of 0.03) were synthesized via the sol-gel route. The samples were sintered at 1250 °C for 6 h to meet single-phase requirements. Confirmation of pure Z-phase ferrite was obtained from the XRD study. Lattice parameters were calculated from cell software. Crystallite size showed a decreasing trend with increasing indium content in the 30 to 26 nm range, while one sample appeared with a size of 37 nm. The maximum cell volume of 1574 (Å3) confirms a successful iron replacement with Indium. Morphological studies via SEM show that hexagonal ferrite with platelet structure is prepared successfully. FTIR analysis at room temperature showed two absorption bands in the 400-600 cm−1 range for octahedral and tetrahedral site vibrations. Various dielectric parameters were studied at room temperature in the frequency range of 1 MHz–6 GHz. The Indium substituted Fe3+ at the octahedral site and reduced ferrous-ferric hooping, reducing the real and imaginary permittivity.
Furthermore, minimum reflection loss of −51.3 dB and −53.9 dB was observed for materials x = 0.06 and 0.12, reflecting that these materials best fit for microwave absorber application. All samples, including EM interference shielding and radar cross-section reduction, are significant for stealth applications. These In3+ substituted Ba3Co2Z Hexa-ferrites might be a good candidate for high-frequency wave applications.
... Ni-Co substituted SrZn 2 W-type hexaferrites were prepared by the co-precipitation method by G.R. Gordani et al. to investigate their use as microwave absorbers [10,16]. Z.J. Su et al. prepared Zn substituted W-hexaferrite applicable for X-band and Ku-band microwave integrated circuit systems [17,18]. ...
Gallium was substituted in Bi0.97K0.9Fe1−xGaxO3 (x = 0.00, 0.04, 0.08, 0.12, and 0.16) and synthesized using a simple citrate sol–gel technique. Structural, magnetic, dielectric, and optical properties were investigated. XRD patterns revealed two intense peaks (110) and (104) merged into a single peak for x = 0.08 and induced structural phase from rhombohedral to orthorhombic symmetry. Cell volume was decreased with the substitution of K-Ga up to x = 0.12. The crystallite size lies in the range of 17.90–45.71 nm. Bulk density was reduced from 2.36 to 2.24 g/cm3 because bigger ionic incorporation resulted in less diffusion at grain boundaries, increasing inner pores. The optical analysis confirmed that the Ga-O bond length was more significant than the Fe–O bond length, and the Fe–O bond length was stretched with Ga incorporation in BKFO. For x = 0.12, dielectric constant and dielectric loss decreased due to the Ga3+ ion’s stable ion yield reduction of Fe3+ at octahedral sites. So, the hopping of electrons between Fe3+ and Fe2+ becomes tricky, and electron accumulation occurs at the interface of grain boundaries which hampers and decreases dielectric polarization. These results suggested that synthesized materials may be applicable in dielectric resonators, magnetic field sensors, and magnetoelectric coupling.
BaMg2TbxFe16-xO27 (x = 0.00, 0.04, 0.08, 0.12 and 0.16) hexaferrites have been synthesized by sol-gel auto combustion method. The synthesized hexaferrites were characterized by structural, spectral, and dielectric properties. As the ionic radii of substituted element Tb³⁺(0.93 Å) is higher than Fe³⁺ (0.64 Å), the lattice parameter ‘a’ increase with substitution while the lattice parameter ‘c' decreases due to internal stresses and lattice distortion. Crystallite size of Tb³⁺ substituted W-type hexagonal ferrites are calculated and found in the range of 13.2–14.95 nm. FTIR patterns confirm the presence of Fe–O bands at octahedral and tetrahedral sites. The variations in the band positions were observed with substitutions of Tb³⁺ content. It is also observed that values of both force constants (Ko and Kt) increase with the inclusion of Tb³⁺ ions, showing the strong intermolecular bonding. The different parameters of dielectric characteristics were examined in the frequency range 1GHz–6 GHz, and these showed variation with Tb³⁺ incorporation and frequency. Dielectric constant, dielectric loss factor, tan loss, and ac conductivity showed an increasing trend while Z′ and Z″ decreases with frequency because conductivity increased. Q value of these materials is low, which may be used in resonant frequency ferrites bead. The obtained results of all parameters including large value of dielectric parameters suggested that these prepared hexaferrites can be used in microwave frequency attenuating devices at GHz, recording, and storage media, and electrical components in mobile phones and refrigerator magnets.
