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Highlights • M-type hexaferrite BaZn 0.6 Sn 0.6 Fe 10.8 O 19 was synthesized at a low sintering temperature of 900 °C. • Rietveld refinement were adapted to make investigated parameters more standard. • This M-type hexaferrite is potential candidate for the design of microwave devices such as circulator operated at Ku band. Abstract M-type barium hexaferrite (BaM) of composition BaZn 0.6 Sn 0.6 Fe 10.8 O 19 was successfully synthesized through a ceramic process. Sintering aids Bi 2 O 3 ·B 2 O 3 ·SiO 2 ·ZnO (BBSZ) were added to lower the sintering temperature. The formation of pure M phase for samples sintered at 900 °C with sufficient BBSZ was confirmed from XRD patterns analysis. Large saturation magnetization (69.02 emu/g) and relatively low magnetic anisotropy field (7.4 kOe) were obtained simultaneously when sample was synthesized with 2.5 wt% BBSZ dosage. These properties make the material suitable for applications in LTCC process. The ferromagnetic resonance (FMR) linewidth (Δ H) decreased efficiently by 719 Oe owing to the sintering aids. This M-type hexaferrite is also potential candidate for the design of microwave devices such as circulators and isolators operated at low frequencies. Meanwhile, the influences of sintering aids upon the microstructure, complex permeability and magnetic properties of M-type hexaferrite BaZn 0.6 Sn 0.6 Fe 10.8 O 19 were investigated. [ABSTRACT FROM AUTHOR]

The BaFe12-xGaxO19 (x < 1.2) hexaferrites were synthesised by usual ceramics technology. The Bi2O3 additive in the amount of 3 wt% was applied. The features of crystal structure and unit cell parameters were refined using powder X-ray diffraction at 300 K. It is shown that with the substitution level increase the parameters of unit cell monotonically decrease. The magnetisation and susceptibility versus temperature and field for these solid solutions were investigated by the vibration magnetometry method. The concentration dependence of the main magnetic parameters is constructed. It is shown that with the substitution level increase the magnetic parameters monotonically decrease. The microwave properties of the samples including the external magnetic bias field are also investigated at 300 K. It is shown that with the increase of Ga3+ concentration from x = 0.1 to x = 0.6 the frequency value of natural ferromagnetic resonance (NFR) decreases in the beginning, and at further increase in concentration up to x = 1.2 it increases again. With the increase in Ga3+ concentration, the line width of the NFR increases that indicates the increase of frequency range where there is an intensive absorption of electromagnetic radiation (EMR). At the same time, the peak amplitude of the resonant curve changes slightly. The frequency shift of NFR in the external magnetic bias field takes place more intensively for the samples with small Ga3+ concentration. It is shown the prospects of use of the Ga-substituted barium hexagonal ferrite as the material effectively absorbing the high-frequency EMR. [ABSTRACT FROM AUTHOR]

Organic inorganic polymer systems were synthesized using ethylene-vinyl acetate copolymer (EVA) as polymer matrix and barium hexa-ferrite (BFO: BaFe12O19) as the inorganic phase by adopting solution casting procedure to ensure better dispersion. The BFO ferrite was first synthesized by the popular sol-gel combustion technique via urea root with ethylene glycol as gelation agent. Rietvelt analysis is performed for the phase quantification, structure refinement of BFO with the XRD diffraction patterns. Once the structure of the BFO is confirmed 0 wt%, 2.5 wt%, 5 wt% and 10 wt% of EVA/BFO polymer inorganic systems were synthesized for the dielectric and electrical investigation in the frequency range 100 Hz-1 MHz. A detailed analysis of the dielectric behavior of the above composites such as dielectric permittivity, dielectric loss tangent (tan δ), dielectric modulus spectra, impedance spectra and electrical conductivity is being reported in this communication. The 5 wt% of BFO in EVA/BFO polymer composite displayed interesting properties than the other wt% composites namely it has high dielectric constant and it showed the relaxation phenomenon in the temperature range of 70-85 °C. The capacitance and resistance values were derived from the simulation of the Nyquist plots with the help of an electrical circuit. [ABSTRACT FROM AUTHOR]

Abstract Carbon can be used as a reducing agent in mechano-chemical reactions in mechanical milling. Some carbon sources have stronger reducing power in comparison to others. In this research mixtures of barium ferrite with different carbon sources (carbon black, graphite and carbon nanofiber) were milled in a high energy mechanical milling machine. The effect of carbon source reducing characteristics on the barium ferrite partial reduction was studied. Phase analysis, particles morphology and magnetic properties were investigated via XRD, HRTEM, and VSM, respectively. Phase analysis showed that the partial reduction of BaO.6(Fe 2 O 3) via carbon black progressed to Fe 1-x O stage in molar ratio of C:O = 1.1 in the milling mixture. Carbon black had the best reducing power and then graphite was better reducing agent compared to carbon nanofiber. The 40 h milled sample with carbon black reached the highest saturation magnetization of 174.65 emu/g after vacuum heat treatment at 900 °C. HRTEM images showed that nanocrystals of Fe 3 O 4 forms after 40 h milling of barium ferrite with graphite. Highlights • Barium ferrite/magnetite nanocomposites synthesized via in-situ partial reduction. • Carbon black, graphite and carbon nanofiber were compared as reducing agents. • Carbon black makes the reduction process of iron oxide to progress to Fe 1-x O stage. • Carbon black had better reducing power than graphite and carbon nanofiber. [ABSTRACT FROM AUTHOR]

M-type barium ferrite, Ba(CoTi)FeO, was synthesized via the solid-state reaction method. BBSZ, i.e., BO −BiO −SiO −ZnO, was added to adjust the sintering temperature to values lower than that of silver (i.e., ∼961 °C). The phase formation characteristics, microstructure, magnetic, and microwave properties were characterized by x-ray diffraction, scanning electron microscope, vibrating sample magnetometer, and impedance analyzer, respectively. The results show that densification of samples were enhanced by increasing the amount of BBSZ with corresponding gains realized in magnetic properties. Such enhanced properties in Ba(CoTi)FeO are attributed to the low-melting point experienced as the result of BBSZ glass additives which gave rise to the stabilization of a liquid phase during sintering. [ABSTRACT FROM AUTHOR]

The present paper reports the influence of cobalt content on the structural, electrical, magnetic and microwave properties of barium hexaferrite synthesized via chemical co-precipitation method. The samples were characterized for their structural, electrical, magnetic and microwave characterizations using XRD, SEM, TEM, VSM etc. The transmission electron microscopy results showed that stacking of nanoparticles of size ~ 50 nm. In addition, the highest saturation magnetization of 29.82 emu/g was observed for composition x = 0.2. The microwave permittivity and permeability decreases with frequency and it varies with the cobalt concentration. Cobalt concentration strongly affects the microwave and magnetic properties of hexaferrite. [ABSTRACT FROM AUTHOR]

Effects of titanium substitution on electrical and magnetic properties of ceramics of barium ferrites having general formula BaTixFe12-xO19, with values of x as 0.00, 0.005, 0.01, 0.02 and 0.03 have been investigated. The compounds are synthesised using two step sintering solid-state rout and characterized by employing SEM and x-ray diffraction. All the titanium substituted compounds show hexagonal single phase symmetry. Gradual loss of saturation magnetization, significant increase in total polarization, rise in value of dielectric constant and upward trend in resistivity are the main parameters observed with titanium substitution on Fe ions. The Curie temperature shows declining trend with dopant concentration. The material is found to exhibit electrical behaviour at expense of its intrinsic magnetic characteristics paving way for Ti ion substitutions for controlled magnetic and electrical properties of barium ferrite. [ABSTRACT FROM PUBLISHER]

A series of W-type hexagonal ferrites with composition BaFe Fe O at different temperatures was synthesized via a ceramic process in a reducing atmosphere during the whole process of calcination and sintering. The phase identification of magnetic powders was performed by X-ray diffraction. The result of XRD confirmed the appearance of a pure phase hexagonal crystal structure with temperature from 1290 to 1330 °C. The microstructures of the magnets were investigated by using a HS-4800 scanning electron microscopy. The magnetic properties of the magnets were measured by a permanent magnetic measurement equipment. B-H curves show that the magnetic properties such as remanence, magnetic induction coercivity, intrinsic coercivity, saturation magnetization and maximum energy product are significantly affected by calcination and sintering temperatures. The optimized sintering and calcination temperatures are 1280 and 1300 °C, respectively. [ABSTRACT FROM AUTHOR]

Citrate precursor method has been used to obtain nanosized particles of barium hexaferrite at low temperatures. Samples were annealed at 450 °C for 3 and 5 h. Quenching of the third sample was done by taking the crucible out from the muffle furnace after annealing it for 5 h and putting it abruptly into an ice bath. The saturation magnetization has been found to be 4.36 and 0.04 emu g for the samples obtained upon annealing at 450 °C for 3 and 5 h, respectively, while that of the quenched sample has been found to be 4.61 emu g. In case of the sample obtained after 5-h annealing, the squareness value was found to be maximum indicating significance in memory and switching applications. For the quenched and the 3-h annealing products, the magnetic data values are similar. Creation of spin disorders on the surface upon prolonged annealing, due to disappearance of oxygen ions and subsequent breakage of superexchange interactions between cations, has been undone upon quenching. The XRD and TEM data indicate that the particle size (9-17 nm) gets lower in case of the quenched samples. Photoluminescence study of the quenched sample furnished prominent peaks in UV, visible and near-IR regions under 200-nm excitation. The TG-DSC data were analysed for the kinetic parameters, activation energy ( E), pre-exponential factor ( A) using the Kissinger isoconversion and the Ozawa-Flynn-Wall methods for the first-step decomposition of the quenched sample. [ABSTRACT FROM AUTHOR]

Barium ferrite and activated carbon were made into a composite to use as photocatalyst for discoloration of organic dyes. The synthetic composite and pure barium ferrite samples were characterized with different techniques. Adsorption studies revealed that the adsorption behavior follows the Langmuir adsorption model and adsorption is favorable in all studied concentrations. The effect of various parameters viz. catalyst synthetic temperature as well as catalyst loading, irradiation intensity and reusability on discoloration reaction was evaluated. More efficient composite was obtained when the synthetic temperature raised from 700 °C to 1000 °C. Additionally, it was noted that degradation increases with increasing catalyst loading from 1 to 10 g/L and particularly with increasing irradiation intensity from 3500 to 26,000 lx, suggesting a photochemical reaction actually occurs. A comparison between the composite and pure barium ferrite showed that activated carbon in the composite structure enhances the photocatalytic activity. The higher activity of composite compared to pure barium ferrite was assigned to higher adsorption affinity of the composite for organic dyes, leading to a synergy between activated carbon and barium ferrite in photocatalytic activity of the composite. The synthetic composite was found to be an effective and reusable photocatalyst against organic dyes. [ABSTRACT FROM AUTHOR]

This work reported a mechanochemically aided sintering process for the synthesis of BaFe 12−x Al x O 19 (x = 0.0, 0.5, 1.0, 1.5, 2.0) hexaferrite ceramic. A brief analysis was conducted on the synthesis mechanism of the pure barium ferrite, its morphology, and magnetic properties. By substitution of Al 3+ ions into BaFe 12 O 19 lattice, the size of the grains decreased and their hexagonal-plate shape tended toward a rod-like shape. These events led to a single domain nature in the grains and also an increase in their magneto-crystalline anisotropy. Single domain nature obtained a barrier against the movement of the domain walls, which led to an increase in coercivity. On the other hand, the increase of anisotropy led to the enhancement of coercivity, according to the Stoner–Wohlfarth model. The substitution of Al 3+ ions also led to the decrease of the saturation magnetization, which was because of the lower magnetic moment of Al 3+ ions (0 μB) compared to that of Fe 3+ ions (+5 μB). As a result of substituting Al 3+ ions with a value of x = 2, a maximum reflection loss of −43 dB was obtained at a frequency of 15.7 GHz. [ABSTRACT FROM AUTHOR]

Porous spherical aggregates of barium hexaferrite (BaFe 12 O 19 ) with 1.5 µm in diameter were synthetized by the surfactant-assisted sol-gel method. The surfactant Tween20 (C 58 H 114 O 26 ), which enables mesoporous structures, as well as polystyrene spheres (PS), as the template agent for the formation of macropores, were used. Two synthetic routes (hereafter named A and B), whose difference was the absence or presence of PS, were followed for synthesis. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) in high resolution mode (HRTEM) were used for characterization. Size and morphology of the spheres were similar in both cases and they resemble a nest or ball-of-yarn type structure. Pore size and BaFe 12 O 19 crystal size produced by the two routes are different. The magnetic properties of the spheres were evaluated using a vibrating sample magnetometer (VSM) as function of the calcination temperature. The spheres present ferromagnetic behavior in both routes. [ABSTRACT FROM AUTHOR]

A series of iron-based perovskite oxides BaFe1− xCu xO3− δ ( x = 0.10, 0.15, 0.20 and 0.25, abbreviated as BFC-10, BFC-15, BFC-20 and BFC-25, respectively) as cathode materials have been prepared via a combined EDTA-citrate complexing sol-gel method. The effects of Cu contents on the crystal structure, chemical stability, electrical conductivity, thermal expansion coefficient (TEC) and electrochemical properties of BFC- x materials have been studied. All the BFC- x samples exhibit the cubic phase with a space group Pm3m (221). The electrical conductivity decreases with increasing Cu content. The maximum electrical conductivity is 60.9 ± 0.9 S cm−1 for BFC-20 at 600 °C. Substitution of Fe by Cu increases the thermal expansion coefficient. The average TEC increases from 20.6 × 10−6 K−1 for BFC-10 to 23.7 × 10−6 K−1 for BFC-25 at the temperature range of 30-850 °C. Among the samples, BFC-20 shows the best electrochemical performance. The area specific resistance (ASR) of BFC-20 on SDC electrolyte is 0.014 Ω cm2 at 800 °C. The single fuel cell with the configguration of BFC-20/SDC/NiO-SDC delivers the highest power density of 0.57 W cm−2 at 800 °C. The favorable electrochemical activities can be attributed to the cubic lattice structure and the high oxygen vacancy concentration caused by Cu doping. [ABSTRACT FROM AUTHOR]

BaFeTbTmTiO ( x = 0−2.5 in a step of 0.5) substituted barium ferrite nanoparticles were synthesized by a sol-gel method. The structural characteristics of ferrite were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, FTIR, andFe Mössbauer spectroscopic measurements. It was found that single-phase barium ferrite nanoparticles with a narrow size distribution were successfully fabricated. The substituted cations were occupied in 12k sites. Vibrating sample magnetometer (VSM) results reflect that with an increase in substitution contents, the coercivity increases, while saturation of magnetization decrease. The reflection loss measurements were carried out on substituted ferrite nanoparticles. The obtained results revealed that the incorporation of Tm-Tb-Ti cations could enhance reflection loss and bandwidth in 8-12 GHz band. The role of matching thickness on the shifts of frequency was also investigated. [ABSTRACT FROM AUTHOR]

Nano-sized barium hexaferrite particles were synthesized by mechanical activation of BaCO 3 and Fe 2 O 3 powders mixture as starting materials. The effects of mechanical milling energy on the phase composition, morphology, thermal behavior and magnetic properties of the samples were systematically investigated by employing X-ray diffractometer, field emission scanning electron microscopy, differential thermal/thermo gravimetry analysis and vibrating sample magnetometer, respectively. The milling energy was calculated at five different levels using collision model. It was found that there is an optimum milling energy value for obtaining barium hexaferrite phase. The results revealed that applying a minimum total milling energy of 93.7 kJ/g was necessary for formation of almost single barium hexaferrite at a relatively low calcination temperature of 800 °C. FESEM micrograph of the above sample exhibited nano-size particles with a mean particle size of 80 nm. Further increase in milling energy leads to dramatic decrease in phase purity as well as magnetic characteristics of the samples. By increasing the milling energy from 93.7 to 671.9 kJ/g, saturation magnetization ( M s ) decreased from 22.5 to 0.39 emu/g, and also coercivity ( H c ) decreased from 4.28 to 1.46 kOe. [ABSTRACT FROM AUTHOR]

Composite films with filler microparticles of Barium ferrite BaFe 12 O 19 (BaFO, 1–20 wt.%) dispersed within P(VDF-TrFE) acting as piezoelectric polymeric matrix have been prepared by solvent evaporation. SEM and TEM images in combination with magnetic measurements clearly probe the good dispersion and random distribution of the BaFO microparticles within the films. Young’s modulus of the fabricated composites remains almost unchanged for all filler contents, indicating that this acts as a small defect within the P(VDF-TrFE) matrix. On the contrary, dielectric properties clearly reduce for low filler contents, 1 and 5 wt.%, and recover and increase their values in a smooth and monotonous way for higher BaFO filler contents of 10 and 20 wt.%. This trend is not followed by the electrical conductivity. Additionally, we have extended the study to fibers composed of BaFe 12 O 19 microparticles within a PVDF matrix. Due to the big size of BaFO particles (about 1 μm in diameter), a proper fabrication of the fiber shaped composites has not been achieved. We found that true BaFO content are always lower than nominal ones. Results are discussed in terms of the influence of size and morphology of the BaFO particles on the initial properties of the pure polymeric matrix. [ABSTRACT FROM AUTHOR]

Micro-nano barium ferrite hollow ceramic microspheres (HCMs) was prepared by low-temperature self-reactive quenching technology combined with heat treatment. Effect of Co(NO) on intrinsic parameters and absorption properties of micro-nano barium ferrite HCMs was investigated. The results indicated that the introduction of Co(NO) modified the intrinsic parameters of HCMs, i.e. the types of phase composition increased, the particle size distribution became broader and the density increased. However, the surface morphology was unchanged. The change of intrinsic parameters after introducing Co(NO) enhanced the permittivity and permeability significantly in the 0.1-18 GHz range. In the range of 2-4 mm of thickness, the minimum reflectivity value of Co-doping HCMs-paraffin composites could reach −31.2 dB corresponding to a thickness of 2.5 mm, moreover, the bandwidth <−10 dB was obtained in 5.4-18 GHz. Generally, we could rationally deduce that the absorption properties of barium ferrite HCMs can be improved significantly by introducing Co, furthermore, it could be modulated by adjusting thickness. [ABSTRACT FROM AUTHOR]

The nanocomposite of hard (BaFe12O19)/soft ferrite was prepared, and then the polypyrrole (PPy)-BaFe12O19/Fe3O4 multi core-shell was produced by in situ polymerisation method. X-ray diffraction, transmission electron microscope, scanning electron microscopy and fourier transform infrared spectroscopy analysis indicated that Fe3O4 coated on the BaFe12O19 ferrite was homogenously enwrapped by PPy coating. The magnetic properties and electrical conductivity of the nanocomposite were characterised by vibrating sample magnetometer and four-wire technique respectively. As prepared conducting ferromagnetic polymer nanocomposites have electrical conductivity of the order of 5 S cm−1 and saturation magnetisation Ms value of 3 emu g−1. Microwave absorbing properties of the nanocomposite were investigated using vector network analysers in the frequency range of 8-12 GHz. The values of the minimum reflection loss were −23 dB at 10 GHz and −28 dB at 11·5 GHz for Fe3O4 coated on the BaFe12O19/Fe3O4/PPy core/shell nanocomposite with a thickness of 1·5 mm. [ABSTRACT FROM AUTHOR]

The effect of gamma irradiation on the features of aluminum-substituted barium hexagonal ferrite particles BaAlxFe12−xO19with 0 ≤ x ≤ 3.5 has been studied. Optical absorption measurements have been performed and the results reflected a great dependence of the fundamental absorption edge on the radiation dose. It is found that the calculated optical band gap (Eg) increases due to an increase in the homogeneity with an increase in the Al content. Increasing the radiation dose up to 1 MGy induces a direct transition and consequently decreases the energy gap. This behavior is associated with the generation of excess electronic localized states. Moreover, the characteristic features of the irradiated samples have been studied using a scanning electron microscope. Also, all samples were characterized using the X-ray diffraction technique, and the values of crystal size, microstrain and dislocation density were calculated. On the other hand, the magnetic behavior of the samples was studied using a vibrating sample magnetometer technique after each radiation dose. The saturation magnetization (Ms) and the magneton number (nB) decrease with an increase in the Al3+substitution and at the same time decrease with the radiation dose 250 kGy to 1 MGy. [ABSTRACT FROM PUBLISHER]

Highlights: [•] The chiral PANI/BF composite is successfully synthesized. [•] Microwave absorbing properties are discussed. [•] The chiral PANI/BF composite can potentially be used as microwave absorbing material. [ABSTRACT FROM AUTHOR]

Plate-like W-type barium ferrites (BaCoZnFe16O27) were prepared by using a combined method of molten salt and a sol–gel process. Pure plate-like W-type barium ferrite with large size about 25 μm and high aspect ratio (diameter/thickness) of ∼35 was obtained at a sintering temperature of 1200 °C. Morphology, phase evolution and static properties of the samples sintered at different temperatures (800–1200 °C) and dynamic magnetic properties of their composites with silicon resin were investigated by using SEM, XRD, VSM and VNA. It was found that the saturation magnetization M s increased with increasing sintering temperature, whereas the coercivity H c decreased. Silicon resin composites filled with 45 vol% of the plate-like BaCoZnFe16O27 particles sintered at 1200 °C exhibited promising microwave attenuation properties. [ABSTRACT FROM AUTHOR]

In this work, we prepared barium ferrite-silica (BaM-SiO2) nanocomposites of different molar ratios by high-energy ball milling, followed by heat-treatment at different temperatures. The microstructure, morphology and magnetic properties were characterized for different synthesis conditions by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). The results indicate that 15h of milling was enough to avoid the generation of hematite phase and to get a good dispersion of barium ferrite particles in the ceramic matrix. For milling periods beyond 15h and heat treatment above 900°C, the XRD patterns showed the presence of hematite phase caused by the decomposition of BaM. The agglomerate size observed through SEM analysis was around 150nm with a good BaM dispersion into the SiO2 matrix. The highest saturation magnetization (Ms) value obtained was 43emu/g and the corresponding coercivity (Hc) value of 3.4kOe for the composition 60BaM-40SiO2 milled for 15h and heat treated at 900°C. This coercivity value is acceptable for the application in magnetic recording media. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, M-type Al-doped barium ferrites were successfully synthesized using sodium citrate (SC) as the chelate agent by a chemical process complemented by a suitable thermal treatment of the precursor. It was found in TGA/DTA and XRD analysis that the crystallization and formation of single phase BaM had completed before 860°C. The XRD data also confirmed Al substituting into Fe sites. Meanwhile, it can be seen from the SEM images that the particle size and morphology were not affected by Al doping. However, Al substitution played an important role on the magnetic properties. The saturation magnetization (M s ) of BaAl x Fe12−x O19 decreased from 51.43emu/g for the sample with x=0 to 28.32emu/g at x=1.5. The anisotropy field (H a ), however, increased from 16.21kOe to 25.01kOe. In addition, M s increased with enhancing the ratio of SC/Ba2+(molar ratio), reaching a maximum when SC/Ba2+ was 13. [Copyright &y& Elsevier]

A hybrid material consisting of thermoelectric BiSb and Ba ferrite BiSb(BaFeO) ( x = 0, 0.025, 0.04, and 0.08) was synthesized using sintering. Powder x-ray diffraction patterns and scanning electron microscopy images of the hybrid indicate that the BaFeO particles were well distributed in the host BiSb phase. The temperature dependence of the electrical resistivity ρ of the host Bi-Sb exhibits metallic behavior. By the addition of Ba ferrite particles, the ρ at 300 K increases intensively, and ρ( Τ) then behaves similarly to a semiconductor. However, it is noted that the thermoelectric power S is unchanged. Inhibition of current and heat flows by a restricted conduction path and the unchanged electromotive force generated by the Seebeck effect in the conduction path can be understood based on a site-percolation model consisting of conducting Bi-Sb and insulating Ba ferrite. The critical volume fraction p of this system was estimated experimentally as p = 0.68. [ABSTRACT FROM AUTHOR]

Abstract: In this research mixtures of barium ferrite and graphite with different molar ratios were mixed and milled in a planetary ball mill to produce a BaFe12O19/Fe3O4 nano-composite. Some of the milled samples were then heat treated at 750 and 850°C under vacuum to synthesize BaFe12O19/Fe/Fe3O4 composite. The effects of graphite content in the mixtures (C:O molar ratio of 0.9, 1 and 1.1), milling time and heat treatment on the characteristics of powder mixtures were investigated by XRD, VSM and TEM. XRD results showed that barium ferrite was partially reduced to Fe3O4 during milling. It was also found that increasing the C:O molar ratio from 0.9 to 1.1 accelerated the reduction process. The results showed that the magnetic properties of the milled and heat treated samples were altered by changing the C:O molar ratio. The saturation magnetization of BaFe12O19/Fe3O4 nano-composite formed in the 40h milled sample with a C:O molar ratio of 0.9 was 27.86emu/g. This value increased to156.40emu/g after heat treatment at 850°C. Increasing the C:O molar ratio from 0.9 to 1.1 increased the saturation magnetization to 169.19emu/g in the heat treated sample. The VSM results also showed that the coercivity of milled and heat treated samples is influenced by C:O molar ratio. The lowest coercivity value of 24.36Oe was obtained in the sample milled for 40h and then heat treated at 850°C. This result is correlated well with the XRD results and confirmed mainly soft magnetic nature of the produced nano-composite. [Copyright &y& Elsevier]

In this research, barium ferrite /magnetite nanocomposites synthesized via a mechano-chemical route. Graphite was used in order to reduce hematite content of barium ferrite to magnetite to produce a magnetic nanocomposite. The effects of processing conditions on the powder characteristics were investigated by XRD, VSM, and HRTEM techniques. XRD results revealed that milling under air and argon atmospheres resulted in the appearance of FeO peaks beside BaFeO peaks after 15 and 20 hrs milling, respectively. The intensity of FeO peaks in the XRD patterns increased by increasing the milling time. VSM studies revealed that saturation magnetization of the 40-hrs milled samples under air and argon atmospheres was 31.25 and 36.42 emu/g, respectively. This difference might be due to more FeO content in the latter sample. By annealing of the 40-hrs milled sample in air, saturation magnetization increased to 139.12 emu/g. [ABSTRACT FROM AUTHOR]

The article presents information on properties and structure of barium ferrites and discusses the method of synthesis of M-type hexagonal barium ferrite powders using sol-gel processes. It mentions ferromagnetic properties of barium ferrites and states that these ferrites contain hexagonal close-packed structure. It mentions the methodology of sol-gel method conducted using thermal gravimetric analysis and differential scanning calorimetry.

Abstract: Cobalt-free perovskite cathode with excellent oxygen reduction reaction (ORR) properties below 800°C is a key material toward wide implementation of intermediate-temperature solid oxide fuel cells. This work reports the phase structure, microstructure and performance of such cathode based on the composite phases of triclinic Ba0.9Bi0.1FeO3-δ , cubic BaFeO3 and orthorhombic BaFe2O4 prepared by sol–gel route. The resultant barium ferrites composite cathode exhibits uniform particles, pores and elements distribution. In particular, favorable ORR properties of this cathode is demonstrated by very low interfacial resistance of only 0.036 and 0.072Ωcm2 at 750 and 700°C and maximum power density of 1295 and 840mWcm−2 at 750 and 700°C. [Copyright &y& Elsevier]

The article discusses the first synthesis of doped barium ferrite single crystal in the Fe2O3-BaCO3-Na2CO3system using the flux growth method. The study uses X-ray crystallographic analysis and scanning electron microscopy to show structure of crystals and determine dopants contents in the crystals, respectively. Results show that single crystal have the same structure and composition as barium ferrite.

Ultrafine BaFe12O19 powders are prepared by sol-gel combustion using glycine gels prepared from metal nitrates and glycine solutions which are ignited in a furnace after drying (220 °C, 1 min) prior to calcination in air at 700-1000 °C. [ABSTRACT FROM AUTHOR]