Studies of structural, magnetic and dielectric properties of X-type Barium Zinc hexaferrite Ba2Zn2Fe28O46 powder prepared by combustion treatment method using ginger root extract as a green reducing agent

Various quantities of ginger (Zingiber officinale) root extract were used to prepare X-type Barium–Zinc hexaferrite with the chemical composition Ba2Zn2Fe28O46. The powders were prepared using a combustion treatment method, being pre-heated at 550 °C for 4 h with the ginger as a fuel, followed by final heating to 900 °C for 5 h and natural cooling to room temperature to obtain Ba2Zn2Fe28O46 hexagonal ferrite powder. The phase composition of heated powder samples was investigated by X-ray diffraction (XRD), indicating the formation of a mixture of X-type and hematite (α-Fe2O3). Up to 82.6%, X-ferrite was formed at 900 °C with 52.5 g of ginger root extract. Dielectric analysis of the prepared samples shows the frequency-dependent phenomena. All samples were hard magnets, with coercivity values (HC) between 262.2 and 318.3 kA m−1, and squareness ratios > 0.5. The sample prepared with 52.5 g ginger root extract possesses the highest value of saturation magnetisation (MS = 33.87 Am2 kg−1) in comparison with the other prepared samples. Therefore, ginger was shown to be a useful natural plant extract as a reducing fuel for the low-temperature synthesis of X-ferrites. The sample prepared with 35 g ginger root extract shows a broad loss tangent resonance peak between 10 kHz and 100 kHz, while other samples show loss tangent resonance peaks between 300 kHz and 2 MHz frequency range.publishe

Design and development of Ga-substituted Z-type hexaferrites for microwave absorber applications: mössbauer, static and dynamic properties

Gallium substituted Z-type Sr3GaxCo2-xFe24O41 (x = 0.0–2.0 in steps of 0.4) hexaferrites were synthesised by the sol-gel auto-combustion process, and sintered at 1150 °C. The structural, morphology, magnetic, Mössbauer, dielectric and microwave absorption properties were examined. XRD results of x = 0.0, 0.4, 0.8, and 1.2 samples show the formation of a single Z-type hexagonal phase. The samples x = 1.6 and 2.0 show the formation of Z and M phases. Hysteresis loops analysis suggest that samples x < 1.6 possess a soft magnetic nature, while the samples x = 1.6 and 2.0 show a hard ferrite characteristics. All samples possess multi-domain microstructures. The composition x = 0.4 [maximum MS = 97.94 Am2kg−1] was fitted with seven sextets (Fe3+) and a paramagnetic doublet-A (Fe3+), while beyond x ≥ 0.8 two more doublets (Fe2+) were observed along with seven sextets in Mössbauer spectra. The maximum values of Fe2+ ions (1.26%) and relative area of paramagnetic doublets (1.91%) were observed for x = 1.6 composition, which is also responsible for the lowest value of MS (69.99 Am2kg−1) for this composition. The average hyperfine magnetic field was found to decrease, whereas average quadrupole splitting was found to increase, with Ga-substitution. The substitution of Ga ions enhanced permeability, dielectric constant, magnetic loss and dielectric loss, in a non-linear fashion. The reflection loss was maximum at lower frequencies for samples x = 0.0 and 0.8, and decreases with frequency. Sample x = 0.8 has maximum reflection loss of −12.44 dB at 8 GHz, a measured thickness of 3 mm, and a bandwidth of −10 dB at 1.18 GHz. The observed absorption has been discussed with the help of the input impedance matching mechanism and quarter wavelength mechanism. The observed coercivity in different samples also influenced microwave absorption which demonstrated potenial in microwave absorber applications.publishe

Magnetic Oxides and Composites II (Materials Research Foundations)

Magnetic oxides have highly interesting applications in the fields of permanent magnets, microwave devices, magnetic refrigeration, sensors, catalysis, and the health sector. This book focuses on the synthesis, characterization, and applications of various perovskites, garnets, manganites, carbon-based metal oxide nanocomposites, nanoferrites, and graphene-metal oxide nanocomposites.Используемые программы Adobe AcrobatМагнитные оксиды находят весьма интересное применение в области постоянных магнитов, микроволновых устройств, магнитного охлаждения, датчиков, катализа и сектора здравоохранения. Эта книга посвящена синтезу, характеристике и применению различных перовскитов, гранатов, манганитов, нанокомпозитов оксида металла на основе углерода, наноферритов и нанокомпозитов графен-оксид металла

Ferrites and ceramic composites

The Ferrite term is used to refer to all magnetic oxides containing iron as major metallic component. Ferrites are very attractive materials because they simultaneously show high resistivity and high saturation magnetization, and attract now considerable attention, because of the interesting physics involved. Typical ferrite material possesses excellent chemical stability, high corrosion resistivity, magneto-crystalline anisotropy, magneto-striction, and magneto-optical properties. Ferrites belong to the group of ferrimagnetic oxides, and include rare-earth garnets and ortho-ferrites. Severa

Gallium-substituted X-type hexagonal ferrites Sr2Co2GaxFe28−xO46: effect of substitution and heating temperature on phase formation and magnetic and dielectric properties

Polycrystalline X-type hexagonal ferrites are investigated regarding phase formation at different temperatures and the effect of partial substitution of Ga3+ for Fe3+ ions in the octahedral and tetrahedral sites of the unit cell. The system of Sr2Co2GaxFe28−xO46 (x ranges from 0.0 to 2.0 in steps of 0.4) was synthesised by the sol–gel auto-combustion technique and calcined between 1200–1300 °C with a temperature of 1300 °C required to be able to obtain a pure X-phase. Lattice parameter a did not alter with partial substitution, suggesting minimum crystal distortion, while the unit cell volume shrank from 2488 to 2465 Å3 due to smaller size of Ga3+. Denser and more agglomerated grains were observed in the samples heated to 1300 °C. Soft magnetic behaviour was seen in all samples and the saturation magnetisation was 63–69 A m2 kg−1 for pure X-ferrites, with low coercivity between 8.5–9.5 kA m−1 (106–119 Oe). Reasonably high Ha and K1 values were observed due to a cone of magnetisation partially aligned along the c-axis, and lower HC, Ha and K1 values were seen for pure X-ferrites, decreasing monotonously with increasing gallium substitution. dM/dH curves for pure X-ferrites indicated one magnetic domain type with restricted domain dispersion, and superior exchange coupling with more gallium substitution. Mössbauer spectroscopy of samples heated to 1300 °C reveals Fe3+ ions in high spin state and probable occupancy of Ga3+ in the octahedral site a = a1+a2. Room temperature (RT) dielectric studies show a significant rise in dielectric constant at low frequencies &lt;50 Hz and in ac conductivity with increasing gallium