BaFe12O19 Phase Research Articles

In-plane hard magnetic BaFe12O19 thin films grown on a-plane Al2O3 112¯0 substrates

Ferrimagnetic barium hexaferrite (BaFe12O19) thin films of varying thicknesses were grown on a-plane Al2O3 112̅0 substrates at elevated temperatures using pulsed laser deposition. X-ray diffraction measurements, Raman spectroscopy, and atomic force microscopy analyses were used to investigate the BaFe12O19 film growth and structure. The results indicate that the formation of an α-Fe2O3 ‘bridge layer’ promotes the growth of a BaFe12O19 phase showing an in-plane uniaxial magnetic anisotropy with an easy-axis of magnetization along the [ 0001 ] hexagonal c-axis direction. The crystallographic relationship between the existing phases is given by BaFe12O19 101̅0 //α-Fe2O3 112̅0 //Al2O3 112̅0. As the thickness increases, the fraction of the BaFe12O19 phase increases further. This is accompanied by a change in grain morphology turning from a columnar to a more elongated shape, where the short axis of the BaFe12O19 grains points along the [ 0001 ] easy axis direction.

Small polaron hopping and tunneling mechanisms in Ba0.9La0.1Fe12O19 hexaferrite ceramic at low temperatures

The correlation between dielectric relaxation and conduction mechanisms in the Ba0.9La0.1Fe12O19 ceramic hexaferrite, at temperatures below 100 K was investigated. The sample was prepared using the conventional solid-state reaction method. X-ray diffraction analysis indicated that the sample is composed of a hexagonal BaFe12O19 phase (lattice parameters a = 5.8778(6) Å and c = 23.170(3) Å) and a small proportion of hematite (α-Fe2O3). The average grain size is 1.48 ± 0.4 μm, with irregular hexagonal and agglomerated grains. The magnetic hysteresis curve shows characteristics typical of ferro and ferrimagnetic materials, with an effective magnetic anisotropy coefficient of 0.960×106 emu/cm3 and an anisotropy field of 1.587×104 Oe. A dielectric relaxation process is observed between 50 and 100 K, with an activation energy of 60.4 ± 0.4 meV and a characteristic relaxation time of 2.09 ×10−10 s, mainly attributed to the electrical behavior of the grains. Two conduction mechanisms were identified: small polaron tunneling (high temperatures and low frequencies) and correlated barrier hopping of electrons (low temperatures and high frequencies). The activation energy for free polaron formation, according to the Komine-Iguchi hopping polarization model, was 7.12 ± 0.02 meV. In the dielectric modulus relaxation process between 30 and 54 K, the activation energy was 40.8 ± 0.9 meV, with a characteristic relaxation time of 2.41×10−10 s. The small polaron conductivity in the grain region was 67.52 meV and 54.0 meV in the grain boundary region. The results highlight that the polarization and conduction mechanisms in this ceramic at low temperatures are dominated by small polaron hopping and tunneling, and emphasize the influence of La3+ doping on the structural, magnetic, and electrical properties of barium hexaferrite.

Influence of calcination temperature and particle size distribution on the physical properties of SrFe12O19 and BaFe12O19 hexaferrite powders

The paper deals with the economic optimisation of ferrite powder preparation during producing hard ferrite magnets. The magnetic properties of ferrites are investigated by replacing feedstock and reducing calcination temperature and particles in the order of tens of microns. The granulates about 8–10 mm in size were calcined for 2 h in the temperature range from 1100 °C to 1300 °C and additionally crushed and milled to an average particle size of about 80–90 µm. The scanning electron microscopy images confirmed the agglomerates of particles with different shapes and sizes in tens of µm. The X-ray diffraction measurements revealed that, besides the SrFe12O19 and BaFe12O19 phases, there was also the presence of 2–39% hematite. The highest values of maximum energy product (BH)max = 930 J/m3 and remanent magnetic induction Br = 72.8 mT were obtained at a calcination temperature of 1300 °C. The Henkel plots confirmed the presence of exchange-coupling and dipolar magnetic interactions at lower and higher magnetic fields, respectively. The strength of interactions was also dependent on the calcination temperature. Replacing strontium with barium led to a deterioration of the magnetic parameters, which were optimal at a lower calcination temperature (1100 °C). This phenomenon was partly overcome by reducing the mean particle size of Ba-based hexaferrites to 45–50 µm.

Synthesis and structural characterization of PVDF-based lead-free ceramic composites

PVDF-based compounds are one of the most promising materials for technological application. In this work, structural and optical techniques have been used to study PVDF-based lead-free ceramic composites, considering the inclusion of the ferroelectric BaTiO3 (BT) and magnetic BaFe12O19 (BHF) and SrFe12O19 (SHF) phases. Results obtained from X-Ray diffraction measurements revealed the formation of the PVDF/ceramic composites with the respective ferroelectric and magnetic phases related to the BT and BHF and SHF ceramics. On the other hand, from the analyses of the Raman and FT-IR spectroscopies, it was possible to confirm the incorporation of the ceramics into the PVDF matrix. It was observed that the β-phase % decreased with the increase of doping content, except for the PVDF/BHF composite, which showed to remains almost constant. The results reveal that the studied hybrid PVDF/ceramic samples could be considered potential candidates for electronic applications.

Synthesis, structural and magnetic study of BaFe12O19/CoFe2O4@CoFe2 nanocomposites

Cooperative effects in hybrid nanocomposites are an interesting field of research. The behavior of magnetic nanocomposites is the result of spatial arrangements of phases and their magnetic correlations through exchange and dipolar forces. Understanding these influences is an important task in order to produce magnetic composites with improved properties. In this work, we present a study on the structural and magnetic properties of nanocomposites made of barium hexaferrite (BaFe12O19) coated either with cobalt ferrite spinel (CoFe2O4) or core-shell CoFe2O4@CoFe2 nanoparticles, i.e. BaFe12O19/CoFe2O4 or BaFe12O19/CoFe2O4@CoFe2. The BaFe12O19 (BFO) phase was produced using the ionic coordination reaction technique and then coated with CoFe2O4 (CFO) nanoparticles synthesized by the polyol method. Several concentrations of the BFO and CFO phases were considered. The BFO/CFO samples were reduced in hydrogen gas, where partial reductions of cobalt ferrite give rise to the alloy CoFe2 (CF). Thus, we produced a new nanocomposite of the type BFO/CFO@CF. These samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and Mössbauer spectroscopy (ME). The XRD and ME analyzes revealed the presence of the phases BFO and CFO, for the non-reduced nanocomposites, and for the partially reduced nanocomposites we found three phases BFO, CFO and CF. TEM images showed that these phases are structurally coupled. Isothermal remanent magnetization (IRM) and direct current remanent demagnetization (DCD) measurements were done and the analyzes through the Henkel and δm plots were performed, providing information about the nature of the interactions among the phases and their magnetic behavior. The samples BFO/CFO and BFO/CFO@CF with the lowest percentage of BFO (∼7 wt%) showed exchange coupling between the phases while the other samples exhibited predominantly magnetic dipolar interactions.

Spring exchange mechanism and temperature dependent magnetic properties of BaFe12O19/CoFe2O4 nanocomposites

Bare BaFe12O19, CoFe2O4, and their nanocomposites with concentration percentage 30–70, 50–50 and 70–30 were synthesized by sol–gel approach. The average crystallite size < D > of bare BaFe12O19 nanoparticles (NPs) was 35 nm which gets reduced with the addition of CoFe2O4 phase and found minimum for bare CoFe2O4 nanoparticles, i.e. 12 nm. Transmission electron microscopy (TEM) image showed the agglomeration of nanocomposites and mean particle size was observed to be 44 nm as estimated from normal size distribution. The ZFC/FC curves exhibited that the blocking temperature TB of all samples lies above room temperature. However, a small broad peak at ∼ 75 K in pure BaFe12O19 NPs is attributed to the surface freezing peak (Tf). The flatness in FC curve at low temperature with the addition of CoFe2O4 phase revealed the strong inter-particle interactions. From M−H loops, the value of saturation magnetization (MS) for Ba70/Co30 was found to be maximum (100.82 emu/g) than their corresponding bare nanoparticles. The higher value of MS showed the presence of exchange spring mechanism in these samples. The coercivity of BaFe12O19 sample was observed to be 4262 Oe which get increased with the addition of CoFe2O4 phase and found maximum for CoFe2O4 (7349 Oe), which shows the hard magnetic nature of CoFe2O4 NPs. However, the smaller value of Bloch’s constant “B” for BaFe12O19 phase (4.8 x10−6K-3/2) showed the strong intra-particle interactions in the core of BaFe12O19 NPs. The dM/dH vs. H curves showed the well-established exchange coupling of both hard and soft magnetic phases for 50% concentration of both phases and may be beneficial for high density recording devices.

Enhanced ferroelectric and ferrimagnetism properties at room temperature in BaTiO3 doped GaFeO3 ceramics

BaTiO3 doped GaFeO3 multiferroic ceramics were prepared by solid state sintering. The influence of BaTiO3 doping on the ferroelectric, ferrimagnetic and dielectric properties of GaFeO3 ceramics was systematically studied. The results show that 0.9GaFeO3-0.1BaTiO3 ceramics exhibit enhanced multiferroic behaviors compared with pure GaFeO3 ceramics. The residual polarization of 0.9GaFeO3-0.1BaTiO3 sample is increased from 0.05 μC/cm2 to 0.14 μC/cm2. The increase of magnetic transition temperature and remanent magnetization is attributed to the formation of BaFe12O19 phase. Our results show that 0.9GaFeO3-0.1BaTiO3 ceramics have potential applications in information storage and provide new possibilities for magnetoelectric applications.

Improvement of magnetic properties through the synthesis of ceramic materials with various weight ratios of BaTiO, BiFeO3, and BaFe12O19 with sol-gel method

Electronic devices designed with multiferroic materials comprising both electrical and magnetic properties are needed for significant memory storage. Several studies have been carried out on multiferroic materials based on BaTiO3, BiFeO3, and BaFe12O19. However, none have obtained optimum multiferroic properties because they still show inadequate magnetic properties, especially energy values. Therefore, this study aims to enhance the mechanical properties of ceramics synthesized by the sol-gel method. The XRD and permagraph tests with metallographic observations using Scanning Electron Microscopy (SEM) were used to enhance the ceramic compounds by mixing powder based on BaTiO3, BiFeO3, and BaFe12O19. Furthermore, the ratio of the weight composition of the materials varied by 1:1:1; 1:2:2; 2:1:1; 1:2:1 and 2:1:2. The result showed that the best magnetic properties were obtained at the weight composition ratio of 1:2:2 with a magnetic energy value of 48.0897x104 GkA/m. Based on SEM analysis, the sample with this weight ratio was dominated by the BiFeO3 and BaFe12O19 phases with high magnetic properties.

Structural and microwave absorption properties of BaFe(12–2x) SnxZnxO19 (x=0.05–1.0) ceramic magnets

A series of single-phase samples with BaFe(12–2x) SnxZnxO19 (x = 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.5, 0.7, and 1.0) compositions were successfully fabricated using a mechanical alloying technique. The ionic positions Zn2+ and Sn4+ occupy the same site as the Fe3+ions occupying tetrahedral and octahedral sites, respectively. Because the radius of Zn2+ and Sn4+ each is greater than that of Fe3+ the lattice parameters and the unit cell volume increased linearly with an increase of x. The co-substitution of Zn2+ and Sn4+ ions to Fe3+ in the main phase of BaFe12O19 changed the magnetic properties of the sample. Both Zn2+ and Sn4+ substituting ions reduced the magneto-crystalline anisotropy constant of the main phase from 2.3 × 106 erg/cc at x = 0.05 to 0.89 × 106 erg/cc at x = 1.0. This reduction, reduced coercivity from 16.34 kOe to 0.47 kOe. The saturation magnetization of the single-phase samples was not significantly decreased. All BaFe(12–2x) SnxZnxO19 samples were capable of absorbing the electromagnetic wave in the x-band frequency range with a single absorption peak. The best reflection loss (RL) of -28.1 dB with the largest bandwidth of 3.1 GHz was obtained in a single-phase sample with a composition of x = 0.35, having an impedance (Zin = 51.54-j3. 69 Ω) close to Zo (50 Ω).

Structural and tunable dielectric properties of cobalt ferrite-based nanocomposites

Nanocomposites C:S-1:4 comprising cobalt ferrite (CoFe2O4), strontium ferrite (SrFe12O19) and C:B-1:4 containing cobalt ferrite (CoFe2O4), barium ferrite (BaFe12O19) were synthesized in weight ratios of 1:4 by chemical co-precipitation route with higher content corresponding to SrFe12O19 and BaFe12O19. Rietveld refinement was employed to confirm the presence of independent CoFe2O4, SrFe12O19 and BaFe12O19 phases. The average crystallite size of CoFe2O4 and SrFe12O19 in C:S-1:4 was observed as 20 nm and 56 nm which depicts an increase as compared to individual components. The observed lattice strain in C:S-1:4 was 0.05% and 0.03% for CoFe2O4 and SrFe12O19. In C:B-1:4, the value of strain was 0.06% and 0.04% for CoFe2O4 and BaFe12O19. Increased lattice strain was observed in the prepared composites. Increase in impedance for the prepared composites was observed from measurements performed in the frequency range 20 –106 Hz. Conduction mechanism was explained by overlapping large polaron tunneling model. Dielectric loss measurements for the prepared composites were observed to decrease establishing their usage in microwave applications.

Synthesis and characterisation of lead free BaFe12O19 –(K0.5Na0.5)NbO3 magnetoelectric composites, and the comparison of various synthetic routes

Polycrystalline lead-free (1-x)BaFe12O19–x(K0.5Na0.5)NbO3 magnetoelectric ceramic composites (x = 10, 20 and 30 wt%) were fabricated for the first time, comparing various synthesis techniques, namely solid state reaction, sol-gel, co-precipitation and citrate combustion methods for the synthesis of the ferrite phase. As well as the four synthesis routes, comparisons were made between uniaxial pressing and cold isostatic pressing of the samples prior to sintering at 1200 °C/2 h. Formation of separate magnetic hexaferrite BaFe12O19 (BaM) and ferroelectric (K0.5Na0.5)NbO3 (KNN) phases in the composites was confirmed using x-ray diffraction. The microstructural features revealed distribution of BaM and KNN grains in all the composite systems. Piezoresponse (PFM) and magnetic force (MFM) modes of scanning probe microscopy (SPM) were utilised to assess responses from piezoelectric and magnetic grains. Localised piezoelectric hysteresis loops were measured on KNN grains in composites made by all four methods. Typical hard magnetic hysteresis loops for BaM were observed exhibiting high coercivity values (up to 281 kA m−1 or 3530 Oe), and those composites made using solid state reaction and citrate combustion methods, which contained no impurity phases, had close to maximum magnetisation values (equivalent to ~70 A m2 kg−1 for the BaM phase). SEM, MFM and magnetisation measurements all suggested that the grain size of the BaM in the composites made using solid state reaction, co-precipitation and citrate combustion methods was around 1 µm, and consisting of single magnetic domains. As a result, it is likely that these samples will exhibit a high degree of magnetoelectric coupling.

A Comparative Study on the Phase Structure, Optical and NIR Reflectivity of BaFe&lt;sub&gt;12&lt;/sub&gt;O&lt;sub&gt;19&lt;/sub&gt; Nano-Pigments by the Traditional and Modified Polyacrylamide Gel Method

Barium hexaferrite (BaFe12O19) nano- pigment is a pigment with high near infrared reflection in the wavelength range of 1400-2500 nm. The BaFe12O19 nano- pigments were synthesized by the traditional and modified polyacrylamide gel method and characterized by thermogravimetric and differential scanning calorimetry (TG-DSC) analyses, X-ray powder diffraction (XRD), fourier transform infrared (FTIR), transmission electron microscopy (TEM), and UV-Visible spectrophotometer. The physicochemical properties of BaFe12O19 nanopigments are strongly dependent on the synthesis route. The introduction of carbon particles into the BaFe12O19 precursor accelerates the formation of BaFe12O19 phase, reduces its particle diameter and changes its color properties. The modified polyacrylamide gel method makes it possible to obtain a high efficient near infrared reflection BaFe12O19 nano- pigments with a solar reflectance SR&gt;90%. The high near infrared reflection makes BaFe12O19 nano- pigments have potential applications in the field of heat shielding.

Structure and magnetic properties of Ba1−xDyxFe12−yZnyO19 synthesized by Sol–Gel auto-combustion technique

Ba1-xDyxFe12-yZnyO19 (x ​= ​0–0.1 and y ​= ​0–1) hexaferrites were produced by the sol-gel auto-combustion technique.In the XRD analyses of all samples, BaFe12O19 phase was observed as the pure state. ZnFe2O4 begins to form at x ​= ​0.02 and y ​= ​0.2 and peak intensities increases with the substution of Dy3+ and Zn2+ cations for the samples sintered at 900 ​°C and 1100 ​°C. As the temperature increases to 1300 ​°C, peaks belonging to BaFe12O19 phase were disappeared and transformed into Ba3Fe26O41 and BaZn1.2Fe16.8O27 phases at x ​= ​0.06 and y ​= ​0.6.Crystallite size decreased with increasing Dy3+ and Zn2+ substitutions for the samples sintered at 900 ​°C and 1100 ​°C. The smallest crystallite size obtained at 900 ​°C, x ​= ​0.06 and y ​= ​0.6.As the amount of substitution elements increase, saturation magnetization (Ms) and remenance magnetization (Mr) values decreased due to the formation of paramagnetic spinel ZnFe2O4 phase for the samples sintered at 900 ​°C and 1100 ​°C.The highest Mr value of 36.1 emu/g was obtained for the pure samples sintered at 1300 ​°C. It decreased sharply to 18.9 emu/g (about 50%) with the substitution of Dy3+ and Zn2+ cations at x ​= ​0.02 and y ​= ​0.2.Dy3+ and Zn2+ substituted hexaferrites sintered at 900 ​°C (x ​= ​0.06 and y ​= ​0.6) exhibited the highest Hc value of 4.84 ​kOe.

Improved structural and magnetic properties of a non-stoichiometry Ba:Fe ratio of barium hexaferrite film

In this study, barium hexaferrite film with different Ba:Fe molar ratios (1:2, 1:4, 1:6, 1:8, 1:10 and 1:12) has been synthesized by a sol–gel method and annealed at a temperature of 800 °C in the air. The structural, morphological and magnetic properties of the films have been analyzed by an X-ray diffractometer, a field emission scanning electron microscope and a vibrating sample magnetometer, respectively. The structural analysis revealed that the film with Ba:Fe ratio of 1:4, 1:6, 1:8 and 1:10 crystallized into single phase of BaFe12O19. The morphology study showed that a film with different Ba:Fe ratios has different grain size and shapes. The magnetic measurement at room temperature showed that the film with Ba:Fe ratio of 1:10 has the highest coercivity, Hc value and the film with Ba:Fe ratio of 1:4 exhibits the highest magnetization saturation, Ms value. Because of their high coercivity values, all of the single-phase films are suitable for permanent magnet and data storage applications.

Tetragonal tungsten bronze/barium hexaferrite room-temperature multiferroic composite ceramics

The spontaneously formed multiferroic composite based on tetragonal tungsten bronze structure was successfully synthesized in the form of ceramics by the solid-state reaction. The crystallization of the ceramics in the tetragonal tungsten bronze structure Ba2SmFeNb4O15 and the presence of a secondary magnetic phase of barium hexaferrite BaFe12O19 were established by structural investigation. The hysteresis behavior describing the polarization as a function of an applied electric field and the high ferroelectric Curie temperature ≈ 417 K evidenced the room-temperature ferroelectric properties of the synthesized material. While the piezoelectric coefficients were determined to be around 1.3 pm/V, the microscopic polar domains of the composite ceramics were established by microelectromechanical study. The hysteresis loop of the magnetization versus magnetic field and the high magnetic transition temperature ≈ 590 K evidenced the ferromagnetic properties of the secondary phase and its presence at room temperature. Moreover, the spatial distribution of the magnetic domains was determined microscopically. In this study, not only the multiferroic properties of the Ba2SmFeNb4O15/BaFe12O19 composites have been studied and presented, but the distribution of the polar and magnetic properties was locally investigated as well.

Impact of Different Set of Precipitants on the Formation of BaFe12O19 Phase Nanomaterials.

This work deals with the preparation of BaFe12O19 materials by soft chemical co-precipitation method using a different set of precipitants namely, (i) NaOH and Na₂CO₃, (ii) NH₂CONH₂ and NH₄OH, and (iii) NH₄HCO₃ and NH₄OH. The influence of these precipitants on the different properties is also investigated by various characterizations. The precipitants used in this work considerably affected the phase formation of BaFe12O19 materials. The thermal analyses reveal the thermal decomposition of the intermediate phase as well as the crystallization of BaFe12O19 phase. Due to the amorphous nature, all the co-precipitated products were annealed for 2 h at 1000 °C. Among the different annealed samples, the NaOH and Na₂CO₃ set of precipitant derived materials exhibit nearly single hexagonal phase of crystalline BaFe12O19 nanomaterials with an average crystalline size of ˜48 nm with a = 0.5888(4) nm and c = 2.320(2) nm. The particle size observed in micrograph was rather much higher than the average crystalline size obtained from XRD for the best sample. The BaFe12O19 nanomaterials studied in the present work have been found potential applications in magneto-optic recording media, biomolecular separations, magnetic carriers for drug targeting, permanent magnet, chip inductors, microwave absorbers, and hyperthermia cancer treatment.

Magnetic properties of BaNixFe12–xO19 (x=0.0–1.0) hexaferrites, synthesized by citrate–gel auto-combustion and sintered by conventional and spark plasma methods

The influence of nickel substitutions on the local structure, dielectric and magnetic properties of Ba hexaferrites is investigated in this study for use as rare earth free permanent magnets and microwave devices, especially. For this purpose, BaNixFe12–xO19 (x = 0.0, 0.2, 0.5, 0.8 and 1.0) powders were prepared by auto–combustion of their citrate–nitrate gels precursor whilst spark plasma sintering and conventional sintering techniques were used in order to prepare BaNixFe12–xO19 sintered ceramics samples. Structure, microstructure, dielectric and magnetic properties of BaNixFe12–xO19 materials were investigated by X-ray diffraction, scanning electron microscopy (SEM), dielectric measurements, Mössbauer spectroscopy and SQUID magnetometry. X-ray diffraction analyses indicated that BaNixFe12–xO19, x = 0.0–1.0crystallized on the hexagonal BaFe12O19 structure and, the lattice parameters a and c, decrease as the Ni content increases. Raman spectroscopy analysis confirmed the formation of the BaFe12O19 phase. The presence of Fe in the +3 oxidation state (Fe3+) and of Ni2+ is confirmed by X-ray photoelectron spectroscopy (XPS). The SEM investigations on BaNixFe12–xO19 powders showed the change of the morphology from a granular-like structure to a platelet-like structure with increasing the nickel content which influences the dielectric and magnetic properties of these materials. Dielectric measurements performed on BaFe12−xNixO19 ceramics showed consistent differences between the two sintering methods. Impedance analysis shows a contribution of grains and grain boundaries in all samples. The Mössbauer spectroscopy results evidenced the five Wyckoff crystallographic iron positions and their site occupancy with respect to Ni substitutions content. The permanent magnet characteristics of the hexaferrites were confirmed by the high values of coercive field (up to ∼ 1.7 kOe) and remanence (∼28 emu/g), while the saturation magnetization values are found up to 95 emu/g at low temperatures and 70 emu/g at room temperature (for x = 0.8). The coercive field, remanence and maximum energy product decrease with nickel content, while the saturation magnetization behaves unmonotonically due to the specific variation of the site occupancy. More insight into the link between local structure and magnetic properties of Ni substituted Ba hexaferrite was given.

Phase Formation Study of BaFe12O19 in Bioactive Glass by Modified Processing Technique.

In this work, bioglass ceramics have been successfully fabricated by the modified incorporation method. In this method, solid-state reaction and conventional glass-melting techniques were employed to separately prepare barium hexaferrite (BaFe12O19: BF) and 45S5 bioactive glass powders. The mixture of BF and 45S5 glass powder was then re-melted at 1300 °C to form base glass. In order to change the prepared glass to glass-ceramic samples, a heat treatment technique was employed at temperatures ranging between 695 and 768 °C. The results confirmed the occurrence of Na6Ca₃Si6O18, BaFe12O19 and Fe₂O₃ phases in prepared glass ceramics. It was found that BF addition caused an alteration in magnetic behavior from soft to hard. For bioactivity assessment, the samples were soaked in simulated body fluid (SBF) for 14 days. An apatite layer was found on the surfaces of glass-ceramics confirming their bioactivity. In addition, biocompatibility was assessed by MTT (3,[4,4-dimethy thiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) assay which showed that the ferrimagnetic bioactive glass-ceramics had good cytocompatibility and no cytotoxicity.

Influence of cobalt addition and calcination temperature on the physical properties of BaFe12O19 hexaferrites nanoparticles

Nano-scale particles of pure Barium hexaferrite ‘BaFe12O19’ and Cobalt added Barium hexaferrite ‘CoxBaFe12O19’, with x = 0.04, 0.06 and 0.1 wt%, were successfully synthesized by the chemical co-precipitation method. The synthesized powder was subjected to different calcination temperatures (T = 850 °C, 900 °C, 950 °C and 1050 °C). X-ray powder diffraction (XRD) clarified that nearly single phase of BaFe12O19 with tiny traces of Fe2O3 phase were obtained when the precursor was calcined at 1050 °C for 2 h. The lattice parameters and unit cell volume were almost unchanged with either Cobalt addition or calcination temperatures. From Debye–Scherrer equation, the crystallite size (D) was found to gradually increase with increasing calcination temperature to reach its maximum values for samples calcined at 1050 °C. The formation of Barium hexaferrite phase was also confirmed from Fourier transform infrared (FTIR) spectra through the existence of strong absorption peaks that appeared between 581 cm−1 and 435 cm−1. The morphology and grain size of the samples were examined using transmission electron microscopy (TEM) technique. Optical properties of the samples were studied through ultraviolet ‘UV’ visible spectroscopy. The optical band gap (Eg) of the samples was obtained from Tauc relation as function of Cobalt addition (x) and calcination temperature (T). Finally, the mechanical properties were examined using Vickers microhardness. The microhardness data revealed that the samples exhibited reverse indentation size effect (RISE). The Elastic modulus (E) and yield strength (Y) for the prepared samples were calculated, in accordance with Vickers microhardness, as function of Cobalt addition. Furthermore, the indentation size effect ISE was analyzed using indentation induced cracked model (IIC). The IIC model was found to be a suitable model for describing the microhardness results of the prepared samples. Time dependent Vickers microhardness was done through indentation creep test at different dwell time (t = 10, 20, 30, 40 and 50 s) and constant applied loads (F = 0.98, 4.90 and 9.80 N). Results clarified that the specimens revealed grain boundary sliding together with dislocation climbs at small loads and a dislocation creep in the operating creep process for greater loads.

Physical Properties of BaFe12O19 Materials Obtained Under Different pH Using Hexamine as Novel Fuel by Auto Combustion Followed by Annealing Route.

Hexamine was used as a fuel for the first time to synthesize BaFe12O19 materials under different pH (2, 6, 8, 10 and 12) condition. Though all the combustion products exhibited mixed phases of mainly γ-Fe₂O₃ and BaCO₃, the annealed (1000 °C for 2 h) powders yielded good quality hexagonal BaFe12O19 phase materials. The optical properties of these materials were investigated by Fourier-transform infrared (FT-IR), near-infrared (NIR), and photoluminescence (PL) spectroscopic techniques. Plate-like shaped sticks/rods of nanometric (~33 to 40 nm) edge sizes of particles are observed for the present BaFe12O19 materials. A considerable improvement in NIR reflectivity of BaFe12O19 materials is noted for the present method than the mechano-thermal solid-state synthesis. The thermal analysis (TGA) and ferromagnetic hysteresis loop (M-H) measurements reveal an important change in weight and magnetic parameters, respectively due to variation in pH. It is found that the present pristine BaFe12O19 materials have feeble antibacterial activity as compared to the reported nanocomposite consists of cotton fabric coated with BaFe12O19 nanoparticles against Gram-negative Pseudomonas aeruginosa bacterium.