Papers by Keyword: Hexaferrite

Abstract: In this paper, a Ba_0.6Sr_0.4Fe_11.50Al_0.50O₁₉/MoS₂ composite with a weight ratio of 1:9 has been successfully created. The Ba_0.6Sr_0.4Fe_11.50Al_0.50O₁₉/MoS₂ was synthesized in HEM for 35 hours before sintered at 1000°C for 5 hours. The Ba_0.6Sr_0.4Fe_11.50Al_0.50O₁₉/MoS₂ composite was characterized using XRD for phase formation, crystal structure, and lattice parameters. Based on the XRD results, the Ba_0.6Sr_0.4Fe_11.50Al_0.50O₁₉/MoS₂ composite has two phases with different crystal structures. SEM characterization for surface morphology and particle size. SEM results show heterogeneous particles, but the particle size is not uniform at 0.2-0.6 µm. Measurements of the dielectric constant and dielectric loss are shown as a function of frequency. VSM is used to characterize samples magnetically. The VSM results show ferromagnetic behaviour in the Ba_0.6Sr_0.4Fe_11.50Al_0.50O₁₉/MoS₂ composite with the value of Mr, Ms, and Hc are about 20 emu/g, 40.769 emu/g, and 4.08 kOe, respectively.

Abstract: Magnetic properties of Co, Ni and Zn substituted barium hexaferrite (BaM) samples prepared by solid state ceramic method were studied. Saturation magnetisation were found higher for Zn-substituted BaM, whereas, coercivity is higher for Co²⁺ and Ni²⁺ ion substituted samples. Anisotropy field for all substituted samples was calculated by the law of approaching saturation. Remanence, squareness and thermomagnetic plot suggest Zn²⁺ ions restricts the magnetic interaction of various sites in BaM.

Abstract: Recent investigation on indium substituted SrFe_11.9In_0.1O₁₉ has shown excellent remanence to the saturation magnetization ratio of much greater than the 0.5 that most suitable for isotropic permanent magnets. In this work, such material SrFe_12-xIn_xO₁₉ (x = 0; 0,05; 0,1; 0,2; and 0,5) with the highest value of remanent magnetization was modified by the co-substitution of Fe⁺³ in SrFe_11.9In_0.1O₁₉ with Mn and Ti ions to reduce the coercivity which suitable for radar absorbing applications. A series of magnetic material with SrFe_11.9-yMn_y/2Ti_y/2In_0,1O₁₉ (y = 0,3; 0,6; 1,0 and 1,2) compositions were prepared by mechanical alloying process. The hysteresis loop for SrFe_11.9-yMn_y/2Ti_y/2In_0,1O₁₉ samples showed that the coercivity was progressively reduced from 300 kA/m for y = 0,6 to 100 kA/m for y = 1.2 with the remanence remained significantly un-changed. The reflection loss (RL) which calculated from S-parameters of vector network analyzers (VNA) has resulted in excellent absorption characteristics of SrFe_11.9-yMn_y/2Ti_y/2In_0,1O₁₉ driven by high remanent magnetization and reduced coercivity.

Abstract: Sr_1-xGd_xCo₂Fe₁₆O_27-δ, (x = 0.05–0.20) was prepared via the proteic sol-gel process. Single-phase W-type hexaferrite doped with gadolinium was synthesized. The ferrite shows ferrimagnetic behavior with high saturation magnetization, low coercive field, low remnant magnetization, and a resistivity greater than 10⁷ Ω·cm. The substitution of Sr²⁺ for Gd³⁺ improved the magnetoelectric properties of the ferrite owing to the increase in the concentration of Fe²⁺ and improvement of electron conduction.

Abstract: Magnetic bioceramics based on hydroxyapatite Ca5(PO4)3OH and particles of the M-type hexagonal (barium or calcium) ferrite (taken in proportions 5, 10, 20, 25, 40 and 50 wt % of M-ferrite) with a high bioactivity and magnetic characteristics providing hyperthermal treatment of oncology diseases has been developed and studied. The phase composition, microstructure, and magnetic properties of the synthesized bioceramics have been determined by using electron diffraction patterns, electron microscope micrograms and Mossbauer spectroscopy. It has been shown that the synthesized biomaterial consists of the biocompatible matrix with the apatite structure into which particles of hexagonal ferrite are incorporated. The Mossbauer spectra for all the samples clearly indicates that the particles of hexagonal ferrite are in the ferromagnetic state and small part of particles in paramagnetic state. The magnetic parameters of the synthesized ceramics are substantially higher than those of the bioglass ceramics modified by iron oxides that have been used in medicine, which suggests good potential and effectiveness of application of the created ceramics for medical purposes. Thus, a new class of magnetic bioceramics combining hydroxyapatite Ca5(PO4)3OH, which exhibits good properties in biocompatibility and bioactivity, with particles of the M-type hexagonal ferrite, which possess high magnetic characteristics, has been created.

Abstract: Barium - Strontium Hexaferrite and Barium Strontium Titanate are both well established materials which widely used respectively as permanent magnets and piezoelectric devices. As the properties are a structure sensitive, materials structure as well as crystal structure must be properly designed to meet a specific application. In this paper, we report our recent investigation on material structure analysis of Ba_0.3Sr_0.7Fe₁₂O₁₉ and Ba_0.7Sr_0.3TiO₃ composite system prepared by a mechanical alloying process to promote feroic properties. The average of particle size for composites system was found initially increased to a large size of 9 μm after mechanically milled for 30 hours and then start to decreased to smaller size of ~ 5μm when the milling time was extended to 80 hours and showing trend toward further reduction in mean particle sizes. In the latter case, the XRD trace for milled powders showed broadened diffracted peaks pattern due to deformation during mechanically milling. After sintering at a temperature of 1050 °C much finer crystallites of 7-13 nm size in a dense pellet were observed. Hence, sintering to the milled particles has promoted formation of nanocrystal containing particles. The mean crystallite size for magnetic phase was about more than 350 times smaller than the mean particle size of composite particles. Finer crystallite sizes were found in B₃SF in which the mean was about 700 times smaller than the mean particle size. The magnetic and electric properties of the composite system are also discussed.

Abstract: Synthesis of Sr₃Zn₂Fe₂₄O₄₁ Z-type ferrite was investigated. Precursors of ferrite were prepared by polymerizable complex method. Identification of formed phases in the obtained samples and determination of lattice parameters of Z-type ferrite were performed by powder X-ray diffraction (XRD). Single-phase of Sr₃Zn₂Fe₂₄O₄₁ Z-type ferrite was synthesized by heating at 1463 K for 5hours in air. M-H curve of prepared single-phase Sr₃Zn₂Fe₂₄O₄₁ Z-type ferrite was measured by using vibrating sample magnetometer (VSM). It was revealed that Sr₃Zn₂Fe₂₄O₄₁ Z-type ferrite has larger saturation magnetization (23.5 μ_B/formula unit) than that of Sr₃Co₂Fe₂₄O₄₁ (22.7 μ_B/formula unit) and shows characteristic two-step saturation of magnetization as well as Sr₃Co₂Fe₂₄O₄₁ Z-type ferrite.

Abstract: Synthesis of U-type hexaferrite was investigated in the various strontium-based systems (Sr-Me-Fe-O system, Me = Co, Zn, Cu, and Ni). Precursors of ferrites were prepared by polymerizable complex method. Sr₄Me₂Fe₃₆O₆₀ (Me = Co and Zn) U-type hexaferrites were synthesized at the temperature range between 1423 and 1483 K in air. Coercivity of obtained ferrite was decreased with increasing heat treatment temperatures. Cu substitution reduced formation temperature of U-type hexaferrite.

Abstract: Nano-size BaM hexaferrites (BaLa0.5Fe11.5O19) were synthesized in the presence of SiO2 nano- particles by sol-gel method. The X-ray diffraction (XRD) patterns of ferrites annealed at above 900°C manifested that all the species had hexagonal crystal structure and no diffraction peaks of SiO2 found. Compared with BaLa0.5Fe11.5O19 powders, those synthesized in the presence of SiO2 nano-particles presented in smaller powder size, as proved by scanning electron microscopy (SEM). As a result, SiO2 nanoparticles promoted the formation of more homogeneous and finer ferrite crystal while the structure of hexaferrites consisted with that synthesized without SiO2 nano-particles. Microwave absorbing properties were evaluated. As a result, BaLa0.5Fe11.5O19/SiO2 showed good microwave absorbing properties with the maximum absorption more than 20dB.

Abstract: New chemical synthesis procedure for the preparation of nickel zinc doped W-type hexagonal barium ferrite and aluminium doped yttrium-iron garnet nanoparticles has been developed, using the nitrate-citrate sol-gel auto-combustion method (NCSAM). The crystalline phase attributes, microstructure, morphology, specific surface area, Curie temperature (TC), permeability, thermal behavior of the as-burnt phase and the heat treated powders were characterized using XRD, SEM, FT-IR, BET, TG-DTA and AC magnetic permeability with frequency shift. In the case of the hexaferrite, the pure W-type ferrite phase is formed during 4 hour annealing at a temperature of 1200 °C, the garnet phase is formed at a lower temperature i.e. 1000 °C. Furthermore it has been confirmed, that the AC magnetic permeabilities of the garnet materials are strongly depending on the chemical composition.