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In the present study, Cu-substituted M-type lead hexaferrites with chemical composition PbCu x Fe 12Àx O 19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) have been synthesized using a co-precipitation method. As-obtained precursors were preheated at 550°C for 4 h in a muffle furnace, followed by final heating at 1150°C for 5 h. All heated samples were cha...
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... m = mass of pellet, M = molecular weight, r = radius of pellet, N = Avogadro's number (6.02 9 10 23 /mol), h = height/thickness of pellet, Z = 2 (for M-type), a and c = lattice constants. The variation of bulk density (d B ), x-ray density (d x ), and porosity (P) with Cu substitution (x) are shown in Fig. 5, and their values are listed in Table ...
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... This is due to the different density of the host and substituted ions; the density of copper ions (8.96 g cm À3 ) is large compared to the density of ferric ions (7.874 g cm À3 ). 57,58 From Table II, it is clear that the values of bulk density are less than the x-ray density, as shown in Fig. 5. The range of bulk density is found from 2.69 g.cm À3 to 4.14 g.cm À3 . The decreasing trend of porosity was observed with copper substitution from x = 0.2 to 1.0 compositions, except for x = 0.8 composition (Fig. 5). In the present case, the systematic variation of the bulk density with a copper substitution is not observed because in ...
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... ions (7.874 g cm À3 ). 57,58 From Table II, it is clear that the values of bulk density are less than the x-ray density, as shown in Fig. 5. The range of bulk density is found from 2.69 g.cm À3 to 4.14 g.cm À3 . The decreasing trend of porosity was observed with copper substitution from x = 0.2 to 1.0 compositions, except for x = 0.8 composition (Fig. 5). In the present case, the systematic variation of the bulk density with a copper substitution is not observed because in real ceramics, the grain growth and porosity are greatly affected by the sintering process. The sample, x = 0.2 shows the minimum value of d B (2.69 g cm À3 ) with a maximum value of porosity (57.09%) compared to ...
Context 4
... m = mass of pellet, M = molecular weight, r = radius of pellet, N = Avogadro's number (6.02 9 10 23 /mol), h = height/thickness of pellet, Z = 2 (for M-type), a and c = lattice constants. The variation of bulk density (d B ), x-ray density (d x ), and porosity (P) with Cu substitution (x) are shown in Fig. 5, and their values are listed in Table ...
Context 5
... This is due to the different density of the host and substituted ions; the density of copper ions (8.96 g cm À3 ) is large compared to the density of ferric ions (7.874 g cm À3 ). 57,58 From Table II, it is clear that the values of bulk density are less than the x-ray density, as shown in Fig. 5. The range of bulk density is found from 2.69 g.cm À3 to 4.14 g.cm À3 . The decreasing trend of porosity was observed with copper substitution from x = 0.2 to 1.0 compositions, except for x = 0.8 composition (Fig. 5). In the present case, the systematic variation of the bulk density with a copper substitution is not observed because in ...
Context 6
... ions (7.874 g cm À3 ). 57,58 From Table II, it is clear that the values of bulk density are less than the x-ray density, as shown in Fig. 5. The range of bulk density is found from 2.69 g.cm À3 to 4.14 g.cm À3 . The decreasing trend of porosity was observed with copper substitution from x = 0.2 to 1.0 compositions, except for x = 0.8 composition (Fig. 5). In the present case, the systematic variation of the bulk density with a copper substitution is not observed because in real ceramics, the grain growth and porosity are greatly affected by the sintering process. The sample, x = 0.2 shows the minimum value of d B (2.69 g cm À3 ) with a maximum value of porosity (57.09%) compared to ...
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Citations
... Substitution or doping with various elements has been investigated to improve the magnetic properties. Among the extensive literature, there are studies involving copper (Cu) as a structural substituent element showing an increase in the magnetization and the coercivity field [4][5][6]. Previously, Banerjee et al. showed that gold enhanced the magnetization of iron oxide nanoparticles [7]. The use of other metals, such as copper, aluminum, and silver, also affects the magnetization and coercivity of SHF [7][8][9][10][11]. ...
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... Fig. 4(F) displays the AC electrical conductivity (σ ac ) of different nanocomposites dispersed in the PVDF-HFP matrix as a function of frequency at room temperature. The Koop and Maxwell-Wagner (MW) models are valuable in explaining the AC conductivity's frequency dependence [60,61]. The electrical conductivity values are obtained by using dielectric data [62], and can be calculated using Eq. ...
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... In all types of ferrites, the value of δ is also higher for the octahedral sites than for the tetrahedral sites [25][26][27][28][29]. Isomer shift for tetrahedral sites (δ TET of f IV ) occupies the 0.251-0.284 mm/s range, whereas for octahedral sites (δ OCT ) the δ value is found in the range of [35][36][37][38][39]. The values of Fe 2+ ions initially increase with the increase in ginger content, and reached a maximum value of 2.7% for the sample made from 35.0 g of ginger root (C), and then decrease again with higher quantities of ginger extract (D and E). ...
... The variation in Fe 3+ and Fe 2+ ions with increasing ginger root extract is shown in Fig. 10 (c). The values of saturation magnetization increased drastically when using the ginger extract Ca hexagonal ferrites [38,40]. In this previously published work on M-type hexaferrites, the α-Fe 2 O 3 impurity was considered at the 2a (↑) site, whereas in the present case, the α-Fe 2 O 3 impurity has been considered at the f VI ↓ site. ...
Download for free for 50 days at: https://authors.elsevier.com/c/1eh8Mvn2L-k8U Ba2Zn2Fe28O46 hexaferrite was prepared using green synthesis with different quantities of ginger root extract (obtained from 0.0, 17.5, 35, 52.5 and 70 g of ginger root) as a natural antioxidant reducing agent. The dried precipitates were preheated at 550 °C/4 h and finally heated at 1200 °C/5 h. The effect of ginger root extract on structural, phase purity, magnetic, Mӧssbauer and low frequency (10 Hz–2 MHz) dielectric properties were investigated. XRD analysis of samples prepared with extracts from 35, 52.5, and 70 g of ginger depicted pure X-phase, while the other samples (0.0, 17.5 g) showed the secondary phase of M-type (BaM, BaFe12O19) along with hematite (12% α-Fe2O3). Hence, samples with greater amounts of ginger extract formed single-phase X-type hexaferrite. Saturation magnetization (MS) varied from 40.8 A m²/kg without ginger extract to 69.8 A m²/kg with extract from 52.5 g ginger, and was <65 A m²/kg for all samples made with the ginger extract. All synthesized samples were relatively soft ferrites, and coercivity increased with amount of ginger extract used. The Mӧssbauer spectra explored six sextets of five magnetic sub-lattices, and the presence of Fe³⁺ (99.4–97.3%) and Fe²⁺ (0.6–2.7%) ions, with more Fe²⁺ present in the extract-derived samples. The variations in MS based on hysteresis loops were in agreement by Mössbauer spectroscopy. The use of the extract also significantly reduced the grain size, from 3.3 μm without ginger extract to 0.7–1.7 μm with the extract, with a corresponding increase in coercivity from 16 to 40–80 kA/m. The samples prepared with extracts from 35 g toand 52.5 g ginger root possessed considerable real dielectric constant compared to the others, but the extract also increased conductivity in the high-frequency region. Complex impedance displayed low values in the high-frequency region, and Cole-Cole plots revealed that the main contribution to conductivity in extract-based samples was from the grains. The reducing action of the green extract not only produced single phase X ferrite, but it also reduced grain size to ∿1–2 μm and greatly increased MS.
... They are also widely used as gas sensors [7][8][9][10], and humidity sensors [11]. The properties of hexagonal ferrites materials are impacted by the different chemical compositions [12][13][14][15][16] and synthesis method used [17][18][19][20][21][22]. ...
... M-type hexagonal ferrites possess the general formula MeFe 12 O 19 , where Me is a divalent metal ion such as Ba 2+ , Pb 2+ or Sr 2+ [30][31][32]. Strontium hexaferrite (SrM-SrFe 12 O 19 ) is the most attractive material because of its widely applications [33]. For example, it is used as a magnetic filler to decrease electromagnetic interference (EMI). ...
... The FTIR spectra of SrFe 12 The band observed at 400-450 cm −1 is representing (ν 2 ) mode because of the ferric ions vibration at octahedral coordination whereas the band observed at ~510-610 cm −1 is owing to (ν 1) mode, representing vibrations of ferric ions at tetrahedral coordination sites. The variation in the position of tetrahedral (ν 1 ) and octahedral (ν 2 ) bands with the different weight ratios of M:S composites are depicted in Fig. 1(b). ...
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SrFe12O19 and NiFe2O4 nano ferrite powders were synthesized in the presence of Calotropis Gigantea (crown) flowers extract separately. SrFe12O19/NiFe2O4 nanocomposites were prepared in the presence of crown flowers extract and the effect of different weight ratios (M:S – 9:1, 8:2, 7:3, 6:4, 5:5) on structural, microstructural, magnetic, electrical transport, and dielectric properties were studied. The average crystallite size of nanocomposites found was from 25 nm to 44 nm. In addition, it was observed that the crystallite size of the M-phase decreased when the spinel phase increased. XRD analysis depicts the presence of both M and S phases in composites. The M-H loops analysis of SrFe12O19/NiFe2O4 composites indicates that the coercivity (3181 Oe to 326 Oe) and saturation magnetization (57.5 Am²/kg. - 40 Am²/kg.) decreased when the spinel phase amount increased. Nanocomposites with weight ratios 9:1, 8:2, 7:3, 6:4 belong to a hard ferrite, while 5:5 shows soft magnetic nature. However, prepared composites possess a multi-domain structure. The weak exchange coupling interactions were found in composites 9:1 and 8:2, whereas the partial exchange coupling interactions were observed in composites 7:3 and 6:4, and perfect exchange coupling interactions were noticed in 5:5.
... Thus, grain size and Sm 3+ content effectively reduce saturation magnetization. The values of squareness ratio (R = M r /M S ) are approximately ≥ 0.5 for all compositions except for x = 0.1, which confirms the single-domain magnetic structure of CoSm x Fe 2-x O 4 nanoferrites [38][39][40]. The larger the grain size, the greater is the flow in the domain movement. ...
Samarium-doped cobalt ferrite nanoparticles CoSmxFe2-xO4 (0≤x≤0.1) were synthesized using citrate gel auto-combustion
method, followed by annealing at 500 °C for 4 h in air. The physical properties of the samples were evaluated using x-ray
difraction, Fourier transform infrared spectroscopy, transmission electron microscopy, Mössbauer, magnetic, and dielectric
measurement techniques. Rietveld analysis of XRD data confrmed the formation of a single-phase cubic spinel structure
for all compositions. Experimental results indicated that doping with samarium (Sm) strongly afected the magnetic properties
of CoSmxFe2-xO4 nanoparticles. The values of saturation magnetization (MS) were reduced from 62.99 (x=0) to 41.17
(x=0.1) emu/g. Room-temperature Mössbauer spectra show two sextets (tetrahedral and octahedral sites), and the values of
the hyperfne magnetic feld (Hhf) of both sextets are found to decrease with Sm-doping. The values of the isomer shift show
that all Fe-ions are found in the Fe3+ state. The interstitial Sm ions positioned within CoFe2O4 realized a dielectric constant
dispersion that displayed a maximum at low frequency. With an increase in samarium ion concentration, the two dielectric
relaxations reached a very wide range of frequencies. This can be attributed to the contribution of conduction in the grains
and grain boundaries of ferrite. Samples with samarium contents of 0.01 and 0.03 showed high impedance stability at 50
and 150 °C, respectively, rendering them suitable for use as a high-frequency window below 1 kHz.
... The energy loss during the conduction of electron between the Fe 3+ ions and Fe 2+ ions in the material can be described by the dielectric loss. The loss factor is calculated by the formula [37] given in equation [7]. ε˝= ε ′ (tanδ) ...
This paper reports the electrical conduction behaviour of Eu³⁺ substituted barium hexaferrites (BaM) prepared via solution combustion method. The structural analysis confirms formation of hexagonal phase of the prepared samples with a space group p63/mmc (No. 194). The SEM micrographs show that the prepared sample has hexagonal plate like structure. Dielectric constant, dielectric loss and AC conductivity of the prepared samples were calculated over a wide frequency range from 10² Hz to 10⁵ Hz at different temperatures. The temperature dependent dielectric studies were also performed over a temperature range of 30°C–200°C. The non –Debye dielectric nature of the prepared samples and presence of electrical relaxation phenomenon were confirmed from the complex impedance spectroscopy. Electrical modulus analysis confirms that there is negligible electrode effect in prepared the samples. From the frequency dependent AC conductivity studies, we find that the AC conductivity values are constant in the lower frequency region and shift towards the higher value in the higher frequency region, which indicates that the prepared samples follow the Almond-West power law. The AC conductivity values decrease gradually with increase in the concentration of Eu³⁺ ions increases. The dielectric studies show that by doping of Eu³⁺ ions, the dielectric constant increases. So the prepared materials can be applicable for microwave devices applications.
... They are also widely used as gas sensors [7][8][9][10], and humidity sensors [11]. The properties of hexagonal ferrites materials are impacted by the different chemical compositions [12][13][14][15][16] and synthesis method used [17][18][19][20][21][22]. ...
... M-type hexagonal ferrites possess the general formula MeFe 12 O 19 , where Me is a divalent metal ion such as Ba 2+ , Pb 2+ or Sr 2+ [30][31][32]. Strontium hexaferrite (SrM-SrFe 12 O 19 ) is the most attractive material because of its widely applications [33]. For example, it is used as a magnetic filler to decrease electromagnetic interference (EMI). ...
... The FTIR spectra of SrFe 12 The band observed at 400-450 cm −1 is representing (ν 2 ) mode because of the ferric ions vibration at octahedral coordination whereas the band observed at ~510-610 cm −1 is owing to (ν 1) mode, representing vibrations of ferric ions at tetrahedral coordination sites. The variation in the position of tetrahedral (ν 1 ) and octahedral (ν 2 ) bands with the different weight ratios of M:S composites are depicted in Fig. 1(b). ...
Strontium hexaferrite (SrFe12O19) powder was
synthesized in presence of Calotropis Gigantea
(crown) flowers extract. The stoichiometric
proportion of strontium nitrate and ferric nitrate were
added one by one in crown flowers extract and heated
at 650º C for 6 hrs to obtain Strontium hexaferrite
powder. Structural properties of calcined powder
were investigated using FTIR and XRD analysis.
FTIR study reveals the formation of ferrite phase.
XRD analysis shows presence of M and α-Fe2O3
phases. The real and imaginary part of dielectric
constant is measured at room temperature between
20 Hz to 2 MHz frequency. The dielectric behaviour
of prepared strontium hexaferrite powder is described
using Maxwell-Wagner bilayer model and Koop’s
theory
