Fig 4 - uploaded by V. Šepelák
Content may be subject to copyright.
Source publication
The response of the structure of the M-type barium hexaferrite (BaFe12O19) to mechanical action through high-energy milling and its impact on the magnetic behaviour of the ferrite are investigated. Due to the ability of the 57Fe Mössbauer spectroscopic technique to probe the environment of the Fe nuclei, a valuable insight on a local atomic scale i...
Contexts in source publication
Context 1
... coordination of oxygen anions. 15 The sextet with a relatively large quadrupole splitting (QS $ 1.1 mm/s), indicating the presence of a large electric eld gradient acting on the iron nuclei, corresponds to Fe 3+ ions in the trigonal bi-pyramidal (2b) sites of BaFe 12 Fig. 3. The mechanically induced evolution of BaFe 12 O 19 was followed by XRD. Fig. 4 shows the XRD patterns of the ferrite milled for various times. The XRD pattern of the starting powder is characterized by sharp diffraction peaks corresponding to BaFe 12 O 19 with the magnetoplumbite structure and space group P6 3 /mmc (JCPDS PDF 27-1029). 9 With increasing milling time, XRD reveals a gradual decrease in the ...
Context 2
... t m ¼ 8 h) is observed, see Fig. 4. Simultaneously, the high-energy milling process leads to the formation of a broad diffraction maximum in the range of about 30-40 (2Q) indicating a partly amorphization of the structure. The superimposition of the relatively broad diffraction reections of the BaFe 12 O 19 phase on a broad diffraction maximum in the range of about ...
Similar publications
The effect of hexadecyltrimethylammonium bromide (CTAB) addition on the crystal structure, morphology, and magnetic properties of co-precipitated hexagonal barium ferrite was investigated. For a fixed amount of surfactant, different Fe 3+ concentrations and Fe 3+ /Ba 2+ ratios were used to optimize the formation of single-phase barium ferrite parti...
Citations
... Crystal structures of the synthesized ceramic materials were determined using the powder X-Ray Diffractometer. XRD patterns of the BIOC materials were given in Fig. 2. Literature data showed that barium ferrite generally had a complex lattice structure (such as hexagonal, octahedral, and tetrahedral) [14][15][16][17]. Thanks to the doping of rare earth element, which acts as a stabilizer [18], this complex crystal lattice structure turned into lattice structure with single uniform and helped to increase the homogenization in the material. ...
Neodymium, gadolinium, and praseodymium doped barium-iron oxide ceramic materials were synthesized by polymeric precursor method. No carbon contents or the moisture was observed in infrared spectra of the ceramics. Neodymium and gadolinium doped ceramics were crystallized in cubic lattice form, while praseodymium doped ceramic was formed in hexagonal lattice. Same results were observed from SEM images, Neodymium and gadolinium doped ceramics had similar morphological structures, but praseodymium doped ceramics had slightly different morphology. Neodymium and gadolinium doped ceramics consisted of grain-like structure, while praseodymium doped ceramic material consisted of both grain-like and pillar-like crystal structures.
... The proximity of the electron cloud in the nucleus region leads to a shift of the nuclear energy level in a compound relative to those in the free atom. A marked change in the isomer shift of the trigonal bi-pyramidal 2b site is noticed when compared to the sol-gel synthesized hexaferrite which may be attributed to the electron density in the environs of the said Fe 3+ ion site [54,55]. The value of isomer shift for the octahedral site is higher than that of the tetrahedral site and hyperfine fields (H hf ) of Fe 3+ ions lying within the S blocks follow the rule δ oct > δ tet and H hf-oct > H hf-tet ., respectively [48,49]. ...
M-type hexaferrite PbFe12O19 nano-crystallites with an average diameter of 68 nm are synthesized by high energy ball milling method. The Rietveld refinement of the X-ray diffraction (XRD) pattern has confirmed the single-phase magnetoplumbite (M) structure of the sample with the space group P63/mmc. Surface morphology is analyzed using transmission and field emission scanning electron microscopes (TEM and FE-SEM). Dielectric studies revealed ferro- to antiferro- and antiferro- to paraelectric transitions. Initial permeability is found to be invariant with temperature and frequency. Small polaron hopping is found to be the prominent conduction mechanism. The room temperature Mössbauer spectrum showed a superposition of five sextets (Zeeman splitting patterns) associated with the five sites of the iron ions, which are ferric (Fe³⁺) state. The values of the hyperfine magnetic fields are found to be 51.12, 50.8, 48.95, 41.15, and 40.11 Tesla corresponding to the 4f2↓, 2a↑, 4f1↓, 12 k↑, and 2b↑ sites, respectively.
... Therefore, the possible interpretation for this reduction in the magnetization of the Li ferrite samples is the core-shell morphology of the nanoparticles. In this model, assuming that the shell thickness d is independent of D and that M = 0 for the shell magnetically "dead", the variation of M s with 1/D will then can be expressed as [56]: ...
... By fitting the magnetization data with the above equation (figure not shown here), the saturation magnetization of the bulk material and the thickness of the shell were estimated to be M 0 = 56.9 emu/ g and d = [56]. V. Sepelak et al. thought that, for non-magnetic nanocrystalline materials, 1 nm is also a typical thickness of grain boundary region [57]. ...
This report, investigates the influence of particle size on the structure, vibration, and magnetic properties of superparamagnetic LiFe5O8 nanoparticles, which is annealed at various temperatures (500, 600, and 700 °C) using a low-cost auto-combustion method. The Li ferrite nanoparticles have been studied using a variety of characterization techniques: powder x-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. The magnetization measurement M(H) at room temperature showed that the annealed ferrite nanoparticles exhibit a superparamagnetic arrangement of single-domain particles due to the structural disturbance in the surface shell of the nanoparticles which is far from equilibrium. We present detailed magnetic measurements such as field cooled and zero field cooled measurements, ac susceptibility, and time decay of magnetization relaxation. Their analysis has been performed using various phenomenological models viz. Néel–Arrhenius, Vogel–Fulcher and power-law model strongly suggests the presence of a spin glass-like behavior in nanoparticles of Li0.5Fe2.5O4. The results presented in this study highlight the key findings that spin-glass behavior of LiFe5O8 is strongly size-dependent. Overall, these samples are excellent prototypes for studying the size effect on magnetic materials and can be used in various technological applications such as magnetic resonance imaging, magnetic hyperthermia, and high-frequency microwave devices.
... The magnetic structure M-type HFs has indirect exchange interaction between magnetic ions and the properties of HFs are influenced by their composition and synthesis methods [92]. M-type HFs have high uniaxial anisotropy [90,[93][94][95][96][97][98][99] [2,107]. The W-type HFs structure can be represented by M-type unit cell and two spinel structure blocks [84]. ...
... The properties of ferrites can be significantly affected by the synthesis method of ferrites. The most popular methods for synthesis of ferrites are sol-gel [2,3,42,68,69,92,94,95,97,98,100,105,106,[112][113][114][115][116][117][118][119] hydrothermal [2,73,77,78,93,[119][120][121][122][123][124][125][126], co-precipitation [2,11,31,79,83,102,104,119,[127][128][129][130][131][132][133][134][135][136][137] and solid-state method [2,64,67,74,76,82,84,89,99,101,103,108,119,[138][139][140][141][142][143][144][145][146][147][148]. Some other methods are also used such as inert gas condensation [119,149], micro-emulsion [119,[150][151][152], electrochemical method [153][154][155], thermal decomposition [156,157], electro-spinning method [2,[158][159][160], etc. for synthesis of ferrites. ...
... X-ray diffraction (XRD) is used to determine the actual crystal structure, crystallite size and strain, phase identification, long range order, unit cell volume, porosity, etc. of ferrites [3,7,9,11,31,42,[68][69][70][71][72][73][74][75][76][77][78]83,84,89,92,94,95,[98][99][100][101][102][103][104][105][106][107][108][112][113][114][115][116][117][118][174][175][176][177][178][179][180][181]. The particle sizes of some of the ferrites via XRD analysis are reported in Table 6. ...
The research on ferrites is fast moving owing to their exponentially growing usage in magnetic shielding, magnetic biosensors, magnetic recording devices, information storage, mobile communication, electronic devices, gyromagnetic device, medical devices, transformers, pollution control, catalysis, and pigments. This review comprises the present state of the art on hexagonal ferrites (HFs) and spinel ferrites (SFs). The article covers the background, properties, classification schemes, synthesis and characterization of ferrites. It focuses on a comparative understanding of four synthesis routes, magnetic properties and characterization of the ferrites. The article emphases X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer, spectroscopy, thermal analysis and vector network analyser results. The present work is meant for the faster understanding of this research area
... This behavior was interpreted in terms of the presence of magnetic dead layer on the surface of a nanoparticle. Similar effect has been seen in different types of magnetic nanoparticles previously, including manganite perovskite and ferrite nanoparticles 89,90 and explained in terms of increasing contribution of surface anisotropy for smaller particles. Hence, a large proportion of dislocations and crystal defects can occur within the lattice and this will cause a reduction of the magnetic moment within the particles, as a result of the magnetocrystalline anisotropy distortion. ...
This article presents the annealing effect on the structural, elastic, thermodynamic, optical, magnetic, and electric properties of Ni 0.6 Zn 0.4 Fe 1.5 Al 0.5 O 4 (NZFAO) nanoparticles (NPs). The samples were successfully synthesized by the sol-gel method followed by annealing of the as-synthesized at 600, 800, 900, 1050, and 1200 C. This approach yielded the formation of a highly crystalline structure with crystallite size ranging from 17 nm to 40 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM) techniques, as well as energy disperse spectroscopy (EDS), Fourier transform infrared (FTIR) and Raman spectroscopy, were used in order to determine the structural and morphological properties of the prepared samples. Rietveld XRD refinement reveals that Ni-Zn-Al ferrite nanoparticles crystallize in inverse cubic (Fd 3m) spinel structure. Using FTIR spectra, the elastic and thermodynamic properties were estimated. It was observed that the particle size had a pronounced effect on elastic and thermodynamic properties. Magnetic measurements were performed up to 700 K. The prepared ferrite samples present the highest Curie temperature, which decreases with increasing particle size and which is consistent with finite-size scaling. The thickness of the surface shell of about 1 nm was estimated from size-dependent magnetization measurements using the core-shell model. Besides, spin resonance, magnetostriction, temperature coefficient of resistance (TCR), and electrical resistivity properties have been scientifically studied and appear to be different according to their size. The optical properties of synthesized NZFAO nanoparticles were investigated, and the differences caused by the particle sizes are discussed on the basis of the phonon confinement effect. This effect was also inspected by the Raman analysis. Tuning of the physical properties suggests that the Ni-Zn-Al ferrite samples may be promising for multifunctional diverse applications.
... In industry ferrites are obtained by conducting a solid phase ferritization reaction at high temperatures followed by grinding in ball mills, so by a mechanochemical synthesis method [8][9][10]. The study of the reaction mechanisms that are the basis of the formation of ferrites points to the complex nature of this process. ...
... Barium hexafferite is a magnetic material with high anisotropy, has a flat hexagon structure, with crystallographic parameters а=5.893 Å та с = 23,194 Å [10,11]. From the established function of particle distribution in diameter, it can be seen that the synthesized barium hexaferrite particles belong to a high dispersive system of crystals with an average particle diameter of <d> = 450 nm. ...
... Taking into account the known fact [8,[10][11][12][13] that the thickness of the structurally defective near-surface layer with distorted magnetic structure for the particles of barium hexaferrite exceeds two parameters of the crystal lattice, the contribution of the near-surface layer in the particles of the experimental system is significant (40-10% of the volume of the particle) to obtain significant results. The determined value of the saturation magnetization of the synthesized sample of barium hexafferite is σs = 64 Аm2/kg and differs from the macro-analogue by 11%. ...
Introduction. The present research was focus to assess the possibilities of the chemical condensation as a method of synthesis of barium hexaferrite nanoparticles for their use in pharmaceutical drugs with magnetic properties. Materials and Methods: For preparation of barium hexaferrite nanoparticles chemical condensation method. Based on the results of previous studies, the methodology of the synthesis and technology has been established. The reaction has been conducted by using solutions of the corresponding metal cations in an alkaline medium. Results and Discussion: Transmission electron microscopy photo shows that the particles of the experimental sample had a plate-shaped hexagonal shape. Most of the particles of the system had a form approximate to the isometric, so for such particles the diameter parameter is twice as large as the thickness (d/h ~2). Synthesized particles do not exceed the upper limit of the single-domain in morphology of a diameter can be used as an object of investigation in a wide range of temperatures and MF parameters such as magnetic properties, interparticle magnetic interaction, and deviation from stoichiometry and physicochemical state of the surface. Conclusion: By the method of chemical condensation the barium hexaferrite nanoparticles with an average particle size = 450 nm and high magnetization σs = 64 Аm²/kg have been synthesized on the basis of which a magnetically controlled X-ray contrast mediums has been developed.
... In the case of x = 0.2÷0.6, the number of components of the spectra signifi cantly increased. Besides the components from hematite and suitable solid solution, five sextets originating from BaFe 12 O 19 compound were fi tted to the spectra (the sextets have B hf values equal to 39.9, 41.1, 48.6, 50.4 and 51.2 T[10]. InFig. ...
In this research, the mechanical activation method is proposed as an alternative process of preparation of the (BiFeO3)1-x-(BaTiO3)x solid solutions with various concentrations of barium titanate (x = 0.1÷0.9). However, mechanical milling itself does not allow obtaining the desired products and additional thermal treatment is needed to complete the solid-state reaction. In the present studies, X-ray diffraction and ⁵⁷Fe Mössbauer spectroscopy were applied as complementary methods in order to study the structural and magnetic properties of materials. The investigations revealed that an increase of BaTiO3 concentration causes changes in the crystalline and hyperfine magnetic structure of the studied (BiFeO3)1-x-(BaTiO3)x system.
... Bereitgestellt von | KIT-Bibliothek Angemeldet Heruntergeladen am | 06.05.17 12:15 allowed for a systematic investigation of structural disorder of mechanosynthesized oxide nanoparticles at the atomic level [68,69,71,72,[74][75][76][77]. For example, the comparative 119 Sn MAS NMR and Raman spectroscopic studies of bulk and nanocrystalline Zn 2 SnO 4 enabled us to separate surface effects from bulk effects of the nanoparticles [68]. ...
... The far-from-equilibrium structural state of the mechanically prepared oxide phases has significant implications for their functional properties. This is exemplarily demonstrated in Figure 20, which compares the magnetization hysteresis loops measured at 5 K for bulk and mechanochemically prepared BaFe 12 O 19 with various crystallite sizes (D) [72]. It is found that the saturation magnetization of BaFe 12 O 19 decreases with decreasing crystallite size from ca. 69 emu g −1 (for bulk BaFe 12 O 19 with D = 220 nm) to ca. 30 emu g −1 (for nanoferrite with D = 14 nm). ...
... Obviously, these large variations in magnetization and coercivity offer an ample opportunity to manipulate and tailor the functional properties of this magnetically hard material. The macroscopic magnetic behavior of the mechanochemically prepared BaFe 12 O 19 is attributed to the effects of the mechanically induced farfrom-equilibrium structural disorder, which is located in the interface/surface regions of the nanoferrite [72]. ...
In many cases, limitations in conventional synthesis routes hamper the accessibility to materials with properties that have been predicted by theory. For instance, metastable compounds with local non-equilibrium structures can hardly be accessed by solid-state preparation techniques often requiring high synthesis temperatures. Also other ways of preparation lead to the thermodynamically stable rather than metastable products. Fortunately, such hurdles can be overcome by mechanochemical synthesis. Mechanical treatment of two or three starting materials in high-energy ball mills enables the synthesis of not only new, metastable compounds but also of nanocrystalline materials with unusual or enhanced properties such as ion transport. In this short review we report about local structures and ion transport of oxides and fluorides mechanochemically prepared by high-energy ball-milling.
... Furthermore, the diffraction peak broadening observed in the milled samples indicates fragmentation of the material and refinement of crystallite size to the nanometer range, as result of the milling process. Similar observation has been reported in the literature [16]. ...
... For BaFe 12 O 19 samples, it was observed that the milling process reduced the average crystallite size to the nanometer range, in agreement to results previously reported in literature [16]. Therefore, there was a reduction from 181.76 nm (starting BaFe 12 O 19 ) to 18.58 nm (20 h milling time). ...
Polymeric composite materials offer advantages for many applications because of a combination of properties, which includes high specific mechanical strength and elastic modulus and corrosion resistance. However, the non-magnetic nature of these materials impedes the use of non-destructive evaluation (NDE) techniques using magnetic sensors. In this work, glass fiber-reinforced epoxy magnetic composites were produced with the addition of 10 wt% of cobalt or barium ferrite particles. Circular plates with notches of 1, 5 and 10 mm in diameter were produced and characterized using magnetic flux leakage (MFL) technique. The effect of particle size on the magnetic properties of the composites was also investigated for the barium ferrite. The results indicated a good correlation between the measured magnetic signals and the presence of notches. Smaller average particle sizes hindered the identification of the smallest notch. However, it resulted in better signal-to-noise ratio for the intermediate and larger size notches.
... These materials are widely utilized as magnetostatic and electromagnetic devices. The M-type ferrite, with the crystal structure similar to that of mineral Magnetoplumbite, and the composition BaFe 12 O 19 , is the best known ferrite [1]. It has a large magnetocrystalline anisotropy, stabilized by the strong exchange interactions among the Fe ions. ...
