Formation Of Barium Hexaferrite Research Articles

Structural, magnetic, and biocompatibility evaluations of chromium substituted barium hexaferrite (Co2–Y) for hyperthermia application

In the present work, chromium-substituted cobalt-based Y-type barium hexaferrite ceramics having a general formula of Ba2Co2Fe12-xCrxO22 (0.0 ≤ x ≤ 0.5) have been studied to evaluate its potential candidacy as an optional replacement for various soft ferrite materials in the field of magnetic hyperthermia. The as-obtained ferrite powders are characterized for structural, magnetic, and morphological properties after being calcined at 1200 °C for 2 h. The structural parameters confirm single-phase nanocrystalline Y-type barium hexaferrite formation within all the samples. The room temperature magnetic parameter, i.e., saturation magnetization (Ms), is found to decrease (from 39.07 to 33.50 emu/g), and the coercive field (Hc) is increased (86.87–281.84 Oe) consistently. Later, oleic acid-coated ferrite samples' heating capability is governed within the applied AC magnetic field (25 mT at a frequency of 114.1 kHz) in terms of specific absorption rate (SAR) using time-dependent temperature performance. The superiority of the sample having the greatest SAR value (84.39 w/g for Ba2Co2Fe11.7Cr0.3O22) is interrelated with the particles' geometry, size distribution, magnetic parameters, and surface chemistry obtained from the XPS analysis. This sample is further analyzed for its biocompatibility performance against the MG-63 cell line; the results indicate that it may be a potential candidate for magnetic hyperthermia due to its significant SAR & ILP value along with better biocompatibility.

Structural, magnetic and microwave absorption properties of doped Ba-hexaferrite nanoparticles synthesized by co-precipitation method

Abstract The structural, magnetic and microwave absorption properties of the barium hexaferrite doped by Zn, Co and Zr cations have been investigated. BaZn x Co x Zr 2 x Fe 12−4 x O 19 ( x =0.0, 0.1, 0.2, 0.3, 0.4, 0.5) nanoparticles were synthesized by the co-precipitation method in the presence of polyvinyl alcohol (PVA). X-ray diffraction (XRD), thermal analysis (TGA–DTA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and vector network analyzer are employed to investigate the desired properties of the prepared samples. From the XRD evaluation it can be seen that the magnetoplumbite structure for all of the samples have been formed and the average crystallite size of nanoparticles lies in the range of 44 ± 3 nm. The TGA–DTA curves of the undoped sample ( x =0.0) indicate that the formation of barium hexaferrite can be obtained at a relatively low temperature of 709 °C. The results of VSM analysis show that the saturation magnetization and coercivity are decreased by increasing the percentage of the dopants. The reflection loss results indicate that the ferrite with the composition of BaZn 0.5 Co 0.5 ZrFe 10 O 19 has appropriate reflection loss (RL

Nanosize Effects on Magnetic Properties and Peak Shifting of X-Ray Diffraction Pattern of BaFe<sub>12</sub>O<sub>19</sub> Produced by Sol Gel Method

The formation of barium hexaferrite, BaFe12O19 single phase with nanosize crystalline is very important to get the best performance especially magnetic properties. The samples were prepared by sol gel method in citric acid-metal nitrates system. Hence the mole ratios of Ba2+/Fe3+ were varied at 1:12 and 1:11.5 with pH of 7 in all cases using ammonia solution. The solution was then heated at 80-90°C for 3 to 4 hours. Then it was kept on a pre-heated oven at 150°C. The samples were then heat treated at 450°C for 24 hours. Sintering process was done at 850°C and 1000°C for 10 hours.Crystallite size was calculated by X-Ray Diffraction (XRD) peaks using scherrer formula. To confirm the formation of a single phase, XRD analyses were done by comparing the sample patterns with standard pattern. The peak shifting of pattern could be seen from XRD pattern using rocking curves at extreme certain 2θ. It was used MPS Magnet Physik EP3 Permagraph L to know magnetic characteristics. This method can produce BaFe12O19 nanosize powder, 22-34 nm for crystallite size and 55.59-78.58 nm for particle size. A little diference in nanosize affects the peak shifting of XRD pattern significantly but shows a little difference in magnetic properties especially for samples at 850°C and 1000°C with mole ratio of 1:12 respectively. The well crystalline powder is formed at mole ratio of 1:11.5 at 850°C since it has the finest particle (55.59 nm) and crystalline (21 nm), the highest remanent magnetization (0.161 T) and the lowest intrinsic coersive (275.8 kA/m). It is also fitting exactly to the standard diffraction pattern with the highest value of best Figure of Merit (FoM), 90%. XRD peak position of this sample is almost same with XRD peak position of another sample with sinter temperature 1000°C at same mole ratio.

Morphology and magnetic properties of barium hexaferrite ceramics synthesized in xwt% NaCl-(100−x) wt% KCL molten salts

Micron size barium hexaferrite (BaFe12O19) platelets were prepared by the molten-salt synthesis method in various weight proportions of NaCl–KCl salt mixtures as a liquid medium. The effect of molten salt composition—x wt% NaCl and (100−x) wt% KCl—on the amount of barium hexaferrite phase formation, as well as, on the morphology and magnetic properties of the final products are discussed. Inductively coupled plasma-mass spectroscopy (ICP-MS) was used to determine the solubility of the starting materials in the salts in order to understand the formation mechanism of barium hexaferrite. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were used to identify the characteristics of the synthesized barium hexaferrite platelets. ICP-MS analysis showed that the Fe2O3 solubility is negligible, however, BaCO3 has very high solubility in both molten KCl and NaCl. Quantitative XRD and SEM results showed that molten salt containing 100 wt% NaCl at 900 °C (for 2 h) resulted in the highest production of barium hexaferrite. Further, SEM results showed that KCl-rich molten salt led to the formation of sharper faceted platelet morphology, whereas NaCl-rich ones resulted in more round platelets. Data from magnetic measurements showed that as the content of NaCl in the molten salt increases, hysteresis losses became higher. This is a characteristic of the achievement of a harder magnetite behavior in the synthesized barium hexaferrite ceramics. The composition of the KCl/NaCl molten salts was shown to play an important role on the extent of barium hexaferrite formation, resulting platelet morphology and the magnetic properties.

The effect of molar ratio on structural and magnetic properties of BaFe12O19 nanoparticles prepared by sol-gel auto-combustion method

Nanocrystalline particles of barium hexaferrite has been prepared by the sol–gel auto- combustion method using iron and barium nitrate with a Ba:Fe molar ratio of 1:10. The effect of fuel such as citric acid and aspartic acid was investigated on the structure and magnetic properties of nanoparticles. The results revealed that the formation of barium hexaferrite fine particles is influenced by molar ratio of metal nitrates to fuel. The formation of pure crystallized BaFe12O19 nanoparticles occurred when the precursor was heat-treated at 900°C for 2 h. Nanoparticles of barium hexaferrite with average crystalline size between 60-69 nm has been obtained. X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were employed to identify the structural phases, surface morphology and magnetic properties of the prepared nanoparticles, respectively. Magnetic measurements showed that the BaFe12O19 nanoparticles exhibited a great coercive field and high saturation magnetization of up to 5100 Oe and 55 emu g -1 , respectively.

FORMATION MECHANISM OF BaFe12O19 NANOPARTICLES PROCESSED VIA WET CHEMICAL ROUTE USING MIXED SOLVENT

Nanosize particles of barium hexaferrite were prepared by co-precipitation route using solution of iron and barium chlorides with a Fe+3/Ba+2 molar ratio of 11. Water and a mixture of water/ethanol with volume ratio of 1:3 were used as solvents. Co-precipitated powders were calcined at various temperatures. XRD results showed that single phase barium hexaferrite forms at 900°C for sample synthesized in aqueous solution and its formation is resulted from the reaction between mainly crystalline phases, while this temperature decreased to 700°C for sample synthesized in water/ethanol solution and the formation of barium hexaferrite consists of reactions between amorphous phases with crystalline phases. SEM micrographs of the calcined samples at 800°C indicated that the morphology of particles was affected by the type of solvent. Nano size particles of barium hexaferrite with mean particle size of almost 80 nm were observed in the SEM micrograph of sample synthesized in water/ethanol solution after calcination at 800°C. Barium hexaferrite crystallites with mean size of 35 nm, which was approximately consistent with size obtained from XRD line broadening technique, could be seen in TEM image of this sample after calcination at 700°C.

One-step synthesis of barium hexaferrite nano-powders via microwave-assisted sol–gel auto-combustion

Single phase barium hexaferrite nano-powders have been innovatively one-step synthesized via a microwave-assisted sol–gel auto-combustion in a specially designed quartz vessel using citric acid and ethylene diamine tetraacetic acid as composite chelating agents and freeze-drying technique to remove sols’ moisture. The auto-combustion product powder is characterized by fluffy particle aggregates with the crystallites ranging from 50 to 100 nm in diameter and containing single magnetic domains for each with a low apparent coercive field of 260 Oe and a high saturation magnetization of 64.1 emu/g. The direct formation of barium hexaferrite is believed to result from the effective improvement in the spatial distribution homogeneity of metal ions and oxidant in the gels. Moreover, the quartz vessel with barium hexaferrite ceramic pad on sample's support and film-strips on its interior wall can effectively build up a favorable temperature environment to promote the direct formation of barium hexaferrite with microwave assistance during the gel's uniform auto-combustion.

Synthesis and magnetic properties of quasi-single domain M-type barium hexaferrite powders via sol–gel auto-combustion: Effects of pH and the ratio of citric acid to metal ions (CA/M)

Quasi-single magnetic domain M-type barium hexaferrite powders have been synthesized via sol–gel auto-combustion route, followed by secondary heating treatment at 800 °C for 4 h, using barium nitrate, ferrite nitrate, ammonium nitrate, citric acid, and ammonia solution as the starting materials. The auto-combustion producing powders were γ-Fe 2O 3 and BaCO 3 with aid of additional ammonium nitrate to increase the combustion temperature. The influences of the citric acid to metal ions (CA/M) and pH values on the gel auto-combustion, the phase compositions of the synthesized powders and their magnetic properties have been studied. The results showed that the chelation of barium and ferrite ions were important for the phase formation of barium hexaferrite: the phase compositions of the synthesized powders changed from a multi-phased mixture to a single phase of M-BaFe 12O 19 for the gradually complete complexing of barium and iron ions with citrate as the pH values and CA/M increased. The resulting powders demonstrated that various magnetic properties mainly depended on the variation in phase composition, sintering adhesion between grains and grown-up of crystalline sizes. With CA/M = 1.5, pH 7, the synthesized powders had a particle size distribution in the range of 100–200 nm and a saturation magnetization of 58.0 emu/g at 12 kOe.

Synthesis of Nano-Crystalline Barium Hexaferrite Using a Reactive Co-Precipitated Precursor

Nano-crystalline particles of barium hexaferrite have been prepared by co-precipitation route using solution of iron and barium chlorides with a Fe/Ba molar ratio of 12 by addition of NaOH with OH-/Cl- molar ratio of 2. A mixture of water and diethylene glycol with volume ratio of 1:3 was used as a solvent in the process. Dried co-precipitated powder was annealed at various temperatures for 1 h. FTIR, XRD, DTA/TGA, SEM, and TEM techniques were used to evaluate powder particle characteristics. DTA/TGA results confirmed by those obtained from XRD indicated that the formation of barium hexaferrite occurs at relatively low temperature of 614 degC for precursor synthesized in diethylene glycol/water solution. The corresponding mean crystallite size measured by TEM for sample annealed at 700degC was 35 nm.

The influence of the coprecipitation conditions on the low-temperature formation of barium hexaferrite

We have investigated the formation of barium hexaferrite via the coprecipitation method. Various reagent salts and solvents were tested, and the coprecipitates were calcined at 300–800 °C for 1–50 h. The samples were characterized with X-ray powder diffraction, electron microscopy and magnetometry. The coprecipitation conditions had a significant influence on the formation time of the barium hexaferrite, which started to form at as low as 500 °C. The optimum coprecipitation conditions were: ethanol as a solvent and chlorides as reagent salts. Powders with optimum magnetic properties, saturation magnetization 60–63 emu/g and coercivity 4–5 kOe, were obtained by calcining at 600–700 °C.

The mechanism of the low-temperature formation of barium hexaferrite

We have investigated the formation of barium hexaferrite via the coprecipitation method. Fine precursor powders were obtained with coprecipitation from water and ethanol solutions of various reagent salts. The coprecipitates were calcined at 300–800 °C for 0–50 h. The samples were characterized with X-ray powder diffraction, thermal analysis, electron microscopy and magnetometry. The formation of barium hexaferrite was a combination of two competing mechanisms and was not influenced by the reagent salts or the solvent. The formation temperature of the barium hexaferrite was reduced to 500 °C by optimizing the coprecipitation conditions.

Processing of nano-structured barium hexaferrite by self-propagating high temperature synthesis (SHS) using nitrate precursor

Barium hexaferrite magnetic powder was produced by self propagating high temperature synthesis (SHS) route through putting a hot filament on top of the compact mixture of iron, iron oxide and barium nitrate powders with a Fe (total)/Ba molar ratio of 12. Morphology, particle size distribution, thermal behavior, phase evolution, chemical analysis and magnetic properties of the products were investigated by SEM, LPSA, DTA/TGA, XRD, EDS and VSM techniques, respectively. EDS analysis confirmed the presence of barium hexaferrite in as-SHS sample. An exothermic peak appeared at 814 °C in DTA/TGA traces seems to be due to the formation of barium hexaferrite. Single-phase barium hexaferrite was formed after annealing of SHS product at 1150 °C for 2 h. SEM micrograph of the sample annealed at 1150 °C for 2 h showed plate-like hexagonal particles of barium hexaferrite with mean size of 2 μm. Saturation magnetization (Ms) and coercivity (Hc) for sample annealed at 1150 °C for 2 h were obtained 66 emu/g and 192 kA/m, respectively. The microstructure of as-SHS sample after it was pressed and then sintered at 1250 °C for 3 h exhibited nano-grains of barium hexaferrite with mean diameter of 200 nm.

Role of intermediate milling in the processing of nano-size particles of barium hexaferrite via co-precipitation method

Nano-crystalline particles of barium hexaferrite (BaFe 12O 19) have been prepared by a co-precipitation/mechanical milling technique using aqueous solutions of iron and barium chlorides with a Fe/Ba molar ratio of 11 and subsequent mechanical milling with a high energy planetary mill. The thermal properties, phase composition and morphology of the products were studied. DTA/TGA results confirmed by those obtained from XRD indicated that the formation of barium hexaferrite occurs at relatively low temperature of 634 °C in co-precipitated/40 h milled sample. The XRD results also showed that intermediate phase of BaO·Fe 2O 3 does not form in milled samples. Nano-size particles of barium hexaferrite with a diameter of 50–100 nm could be observed in the SEM micrograph of co-precipitated/40 h milled sample after calcination at 800 °C for 1 h. SEM micrographs of the samples calcined at 1100 °C for 1 h exhibits hexagonal plate-like particles of barium hexaferrite; an intermediate milling resulted in decreasing of mean particle size from 1.3 μm to 750 nm.

Influence of Fe/Ba molar ratio on the characteristics of Ba-hexaferrite particles prepared by sol–gel combustion method

Nano-crystalline particles of barium hexaferrite (BaFe 12O 19) have been prepared by a sol–gel combustion technique using nitrate–citrate gels prepared from metal nitrates and citric acid solutions under various Fe/Ba molar ratios of 10, 11 and 12. The thermal decomposition process of the nitrate–citrate gels and as-burnt powders was investigated by XRD and DTA/TGA techniques. The results revealed that the nitrate citrate gels exhibit a self-propagating behavior after ignition and the single-phase barium hexaferrite formation temperature is significantly influenced by Fe/Ba molar ratio. The Fe/Ba molar ratio of 11 is more favorable for formation of barium hexaferrite. The SEM investigations revealed that the mean particle size of barium hexaferrite dramatically increases with increasing calcination temperature from 1000 to 1100 °C. The magnetic properties measured using a vibrating sample magnetometer (VSM) revealed that the sample synthesized under Fe/Ba molar ratio of 11, exhibits higher saturation magnetization in comparison with those synthesized under Fe/Ba molar ratios of 10 and 12.

The effect of SiO2 and Cr2O3 additions on the crystallisation behaviour and magnetic properties of a B2O3–BaO–Fe2O3 glass

Abstract Differential thermal analysis, X-ray diffractometry and scanning electron microscopy with energy dispersive spectroscopy were used to study the crystallisation of a glass with a composition of 45% BaO, 30% B 2 O 3 and 25% Fe 2 O 3 (mol%), to which 10–30% SiO 2 was added replacing B 2 O 3 . The effect of 1 mol% Cr 2 O 3 as a nucleation agent also was studied. The magnetic properties of some specimens also were measured with a vibrating sample magnometer. It was found that while the addition of >10 mol% SiO 2 prevented formation of barium hexaferrite, the main magnetic phase, Cr 2 O 3 , greatly enhanced surface crystallisation. All specimens revealed glass in-glass phase separation, which in the presence of Cr 2 O 3 was more extensive and on a much finer scale. The latter specimens, in the form of pressed glass frits heat treated 1 h at 723 °C, showed a coercive force of H c =4150 Oe and saturation magnetisation of M s =9.92 emu/g.

The effect of mechanical milling on the solid state reactions in the barium oxalate–iron(III) oxide system

Abstract The formation of barium hexaferrite, BaFe 12 O 19 , from a 1:6 molar ratio mixture of barium oxalate and iron oxide has been investigated. Thermogravimetry (TGA), high temperature X-ray powder diffraction (HT-XRPD), differential scanning calorimetry (DSC) and micro-Raman spectroscopy have been used to determine the effect of mechanical activation on the solid state reactions occurring during heating. The resulting magnetic properties were investigated measuring hysteresis loops. For the activated mixtures, the mass loss is over at ≈600 °C i.e. well below the temperature where BaCO 3 spontaneous decomposition is complete ( T >850 °C). Such a noticeable temperature lowering is a consequence of the high energy milling enhancing the formation of BaFe 2 O 4 . After heating the milled mixture to 850 °C, BaFe 12 O 19 was rapidly formed from the BaFe 2 O 4 and residual Fe 2 O 3 . Starting from an unmilled mixture, only minor amounts of BaFe 12 O 19 were formed by heating to 850 °C. The favourable formation of barium hexaferrite, when starting from milled powders, has been confirmed by micro-Raman spectroscopy. The powder from the activated sample was shown to have far better magnetic properties than the unactivated sample.

Topochemical Memory Effect in the Formation of Barium Hexaferrite

The topochemical memory effect in Ba(NO3)2 : Fe2O3 = 1 : 6 reaction mixtures containing α-Fe2O3 with different particle sizes was studied at low (540–630°C; the main reaction product BaFe2O4) and high (900–930°C; the main product, BaFe12O19) reaction temperatures. The results indicate that the particle size of Fe2O3 has a significant effect on the BaFe2O4 yield in the low-temperature solid-state reaction ( 585°C). In the subsequent high-temperature solid-state reaction (900–930°C), the BaFe12O19 yield depends on the particle size of Fe2O3 , regardless of the initial reaction temperature. It is shown that, to achieve a high BaFe12O19 yield, the process conditions should be optimized in both the low- and high-temperature stages.

Influence of stoichiometry and alkalinity on barium hexaferrite formation via the supercritical water crystallization method

Fine particles of barium hexaferrite were prepared from aqueous solutions of iron nitrate, barium nitrate and potassium hydroxide by utilizing a continuous flow type supercritical water crystallization method. The influence of stoichiometry (Fe/Ba mole ratio) and alkalinity (R) on the product composition and morphology was studied under fixed temperature, pressure and residence time. Experiments were performed with varying Fe/Ba mole ratios and alkali mole ratio (R). Within mole ratio ranges of 0.5< Fe/Ba< 5, BaO-6Fe2O3 single phase was produced; and as the Fe/Ba mole ratio increased, α-Fe2O3 was also formed and its quantity increased with increasing mole ratio. At an Fe/Ba ratio of 12, stoichiometric mole ratio of BaO-6Fe2O3, the only product formed was α-Fe2O3 fine particles. In the case of the influence of alkalinity, single phase α-Fe2O3 was detected at R of 0.5 and if R exceeded 2, a single phase BaO-6Fe2O3 was detected. According to the results of the experiment and the study of reaction mechanisms, the formation of BaO-6Fe2O3 proceeds via a non-stoichiometric reaction and the product composition and morphology can be controlled by adjusting the reaction parameters to obtain optimum conditions for Ba(OH)2 precipitate formation.

Synthesis of barium hexaferrite by the co-precipitation method using acetate precursor

Fine particles of barium hexaferrite were synthesised by a chemical co-precipitation method using acetate-nitrate (barium acetate + iron nitrate) precursors. The thermal properties, phase composition and morphology of hexaferrite powders were studied. Simultaneous DTA/TG results confirmed by those obtained from XRD and VSM, indicated that the formation of barium hexaferrite occurs at a relatively low temperature of 710°C. This temperature is affected by the Fe3+/Ba2+ molar ratio. The SEM investigations revealed that the mean particle size of barium hexaferrite increases with increasing calcination temperature. In this system the Fe3+/Ba2+ molar ratio of 12 (stoichiometric ratio) is favourable.

Hydrothermal synthesis of barium hexaferrite

The authors of the report carried out synthesis of barium hexaferrite (BHF) both in water vapor atmosphere and in liquid medium in the temperature range 200-400°C at pressures PH2O of 9-26MPa in laboratory autoclaves. The results of research have shown that BHF with the best performances can be obtained by thermovaporous treatment of dry mixtures of precursors (γ-F2O3 with barium hydroxide or nitrate). As Fe - containing precursor, α-FeOOH can be also used. The formation of BHF begins at the temperature of about 200° C. The BHF crystals are hexagonal platelets with diameter ≥ 1 μm and thickness 0,1 −0,2 μm. The magnetic properties of synthesized BHF can be improved by increasing the temperature of thermovapor treatment. The coercive forces of the BHF samples synthesized at about 400°C vary from 1.7-2.0 kOe and spec& saturation magnetization of nonoriented samples from 40-50emu/g. BHF crystals with low coercive force (0.6-0.7) kOe were obtained by introduction of doping micro-additives at the stage of their formation in water vapor atmosphere.