Effect of treatment conditions on structure and magnetodielectric properties of barium hexaferrites (original) (raw)
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Structural and magnetic properties of barium-gadolinium hexaferrites
Journal of Magnetism and Magnetic Materials, 2007
A series of Gd-substituted M-type barium hexaferrites has been prepared by the ceramic route, according to the formula (Ba 1Àx Gd x )O Á 5.25Fe 2 O 3 (x ¼ 020:30). XRD analysis revealed that all the samples present primarily an M-type structure. Samples x ¼ 0 and x ¼ 0:05 are single-phase. Hematite (Fe 2 O 3 ) and GdFeO 3 were detected in the remaining samples. Coercivity (H c ) shows remarkably high values, $293 kA/m for x ¼ 0:20 and 0.30 with a maximum of 322 kA/m for x ¼ 0:25. Specific saturation magnetization (s sat ) of the samples presents a small increase up to x ¼ 0:10. The microstructure examination indicates that Gd may act as a grain growth inhibitor. r
Enhanced Magnetic Properties of Barium Hexaferrite
Journal of Electronic Materials, 2020
Samples having the composition BaFe 12À2x Co x Sm x O 19 (x = 0.0, 0.2, 0.4, 0.6) are prepared by a WOWS (without water and surfactants) sol-gel technique, and the structural, morphological, and AC and DC electrical and magnetic properties of the samples are investigated. The phase formation of M-type hexaferrite is studied by using indexed x-ray diffraction patterns. Scanning electron microscopy images show that the particle size of the synthesized nanopowder varies from 295 nm to 440 nm. The dielectric constant (e¢) exhibits a decreasing trend while the dielectric loss (tan d) increases with increased doping. DC electrical resistivity (q DC) is investigated in a temperature range of 373-673 K and indicates an increasing trend with doping. The magnetic hysteresis loops reveal an increase in saturation magnetization (M s) and remanence (M r), and a decrease in coercivity (H c), with the increase in doping content.
Ceramics International, 2021
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Improving magnetic properties of barium hexaferrites by La or Pr substitution
La or Pr substituted barium hexaferrites, Ba1−x(La or Pr)xFe12O19, x=0.00–0.20, were successfully prepared by a citrate combustion process. The sintered bodies were structurally and magnetically studied by powder X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). All XRD patterns show the single phase of the magnetoplumbite barium ferrite without other intermediate phases. Magnetization (MS) and coercive field (HC) could be improved by substitutions of La or Pr ions on Ba ion basis sites. The MS reveal magnetic behavior with respect to La or Pr ions content, showing an increase at first and then a decrease. The HC increases remarkably with increasing La or Pr ions content.
Influence of Zn–Nb on the Magnetic Properties of Barium Hexaferrite
Abstract In the present study, BaFe12-2xZnxNbxO19 (x = 0. 2, 0.4, 0.6 and 0.8) hexaferrites were prepared by the solgel technique and subsequent thermal treatment. The crystal structure, grain size, and magnetic properties were studied by means of X-ray diffraction (XRD), high-resolution scanning electron microscope (HR-SEM) and vibrating sample magnetometer (VSM). The X-ray diffraction analysis showed that the barium hexaferrite with small substitutions still maintained a hexagonal magneto-plumbite phase. It was found that the mean size of the grains increased with increasing substitution. The saturation magnetization increased slightly with increasing x, which was attributed to different preferential site occupation of Zn–Nb at low and high concentration ranges. The coercivity decreased with increasing x. Structural and magnetic characterizations of these ferrites provide significant information about their reactive physical properties.
Applied Physics A, 2020
In this research project a series of chromium substituted barium hexa-ferrites with formula BaCr x Fe (12-x) O 19 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) have been synthesized using powder metallurgy route, sintered at 1100 °C for 2 h. The structural, functional analysis, surface morphology, magnetic and ferroelectric properties have been investigated using X-ray diffractometer, Fourier infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometer, and ferroelectric technique, respectively. The structural analysis reveals the formation of barium hexaferrite structure with minor secondary phase of Hematite α-Fe 2 O 3 in first five samples. Surface morphology shows that all grains have definite grains shape and grain boundaries. VSM analysis revealed the antiferromagnetic loops due to existence of hematite phase in (x = 0 to x = 0.5) samples, whereas the sample (x = 0.6) shows the ferro-magnetic behavior. Ferroelectric measurement shows centrosymmetric and non-centrosymmetric orientation and maximum remnant polarization due to presence of more Fe 2+ ions in (x = 0.1-0.5) so that not proper closing of first five samples enhanced the magnetoelectric (ME) coupling.
Magnetic and structural properties of M-type barium hexaferrite prepared by co-precipitation
Journal of Magnetism and Magnetic Materials, 2007
Stoichiometric and single-phase barium hexaferrite (BaM) has been synthesized by co-precipitation and an additional solid state preparative method using high-purity nitrates, oxides and carbonates of iron (III), barium (II) and ammonium hydroxide. The isochronally and isothermally measured permeability and magnetic loss tangents over 1 MHz-1 GHz in frequency remained moderately constant until a sintering temperature of 1300 1C where relative permeability of 1.3 and loss tangent of 0.06 at 1 GHz, indicate highfrequency magnetic characteristics for BaM. TGA/DTA studies showed the hexaferrite formation temperature was found to be 1050 1C. The apparent densities before and after each firing cycle showed a monotonic increase. X-ray diffraction studies established the presence of a single phase with the theoretical space group P63/mmc, and computed cell parameters of a ¼ b ¼ 5.895 Å and c ¼ 23.199 Å. The samples exhibited a Curie point (T c) of 452 1C and displayed ferromagnetic resonance characteristics centred on a frequency of 500 MHz.
Influence of Mn addition on magnetic and structural properties of barium hexaferrite
AIP Conference Proceedings, 2013
Two-phase nano-powders based on Ba hexaferrite with addition of Mn have been obtained by a sol-gel autocombustion method. Composition dependence of magnetic and structural properties has been studied using magnetic measurements, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The observed decrease of saturation magnetization and coercivity with increase of Mn content is mainly attributed to the presence of Fe oxide as a result of Ba depletion. SEM images show chemically homogeneous, non-regular shaped agglomerated nano-particles (50-200 nm).
Materials Letters, 2014
Rod, platelet and ellipsoidal nanostructures of BaFe 12 O 19 have been synthesized by the Pechini method followed by heat treatment. The produced samples were heat treated at 900 1C for different hours and characterized by X-ray diffraction, scanning electron microscopy, Mössbauer spectroscopy and vibrating sample magnetometry. The results showed that the particle size and morphology vary with the time of heat treatment. The samples consisting of nanoparticles with different morphologies exhibited plateaus in the magnetic hysteresis loops.