Influence of Mn addition on magnetic and structural properties of barium hexaferrite (original) (raw)
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Barium hexaferrite powders of nanometer particle size synthesized via two variants of the microemulsion technique, namely, single microemulsion and double microemulsion, were studied. The influence was explored of the type of microemulsion technique on the microstructure and on the magnetic properties of the barium hexaferrite powders. The average particle size of the barium hexaferrite powders was in the range from 110 nm to 442 nm depending on the method and conditions of synthesis. The particles with size below 150 nm had irregular shapes between spherical and platehexagonal; the bigger ones had an almost perfect hexagonal shape. The powders obtained by single microemulsion had better magnetic characteristics (saturation magnetization of 65.12 emu/g and coercivity field of 3.6 Â 10 5 A/m) than those obtained by double microemulsion.
Influence of synthesis variables on the properties of barium hexaferrite nanoparticles
Journal of Materials Science: Materials in Electronics, 2016
Barium hexaferrite (BaFe 12 O 19) nanoparticles were synthesized by sol-gel auto-combustion route. Prepared samples were sintered at 950 and 1100°C with Fe 3? / Ba 2? = 12 and 20 mol ratio. The formation mechanism of barium hexaferrite was investigated by using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses. In addition, the effect of temperature and Fe 3? /Ba 2? mole ratio on BaFe 12 O 19 formation and magnetic properties, and the effect of increasing the Fe 3? /Ba 2? upon gel ignition and subsequent phase development were investigated. Finally the magnetic behavior was monitored with VSM. DSC studies showed that pure barium hexaferrite phase was formed from maghemite (c-Fe 2 O 3), without the formation of hematite (a-Fe 2 O 3). Also, XRD results confirmed the formation of barium hexaferrite phase in non stoichiometric Fe/Ba ratio. VSM results showed that the saturation magnetization was decreased and coercivity increased with decreasing the grain size.
Journal of Magnetism and Magnetic Materials, 2011
Barium hexaferrite BaFe 12 O 19 powders have been synthesized using the modified co-precipitation method. Modification was performed via the ultrasonication of the precipitated precursors at room temperature for 1 h and the additions of the 2% KNO 3 , surface active agents and oxalic acid. The results revealed that single phase magnetic barium hexaferrite was formed at a low annealing temperature of 800 1C for 2 h with the Fe 3 þ /Ba 2 þ molar ratio 8. The microstructure of the powders appeared as a homogeneous hexagonal platelet-like structure using 2% KNO 3 as the crystal modifier. A saturation magnetization (60.4 emu/g) was achieved for the BaFe 12 O 19 phase formed at 1000 1C for 2 h with Fe 3 þ /Ba 2 þ molar ratio 8 using 5 M NaOH solution at pH 10 in the presence of 2% KNO 3. Moreover, the saturation magnetization was 52.2 emu/g for the precipitated precursor at Fe 3 þ /Ba 2 þ molar ratio 12 in was achieved for the precipitated precursor ultrasonicated for 1 h and then annealed at 1200 1C for 2 h. Coercivities from 956.9 to 4558 Oe were obtained at different synthesis conditions.
Journal of Materials Research, 2006
We report studies on the correlation between the microstructure, the magneto-crystalline structure, and the magnetic properties of barium hexaferrite powders. The samples consisted of typical hexagonal plate-like particles with approximate sizes of 80, 180, and 500 nm, obtained by microemulsion, coprecipitation, and solid-state reaction techniques, respectively, and were characterized by x-ray powder diffraction and scanning and transmission electron microscopy. The hyperfine parameters of the hexaferrite powders with different particle size were investigated by Mössbauer spectroscopy. We also measured the magnetization-versus-magnetic field dependence of the submicron powders at high magnetic fields up to 30 T at 4.2 K. Finally, we comment on the surface effects observed because of particle size reduction from micron to nanoscale dimensions.
Nano-Crystalline Barium Hexaferrite Powders Prepared by Mechanical Alloying Using Acetate Precursor
Nano-crystalline barium hexaferrite powders have been prepared by mechanical alloying of nFe 2 O 3 +Ba(CH 3 COO) 2 with Fe/Ba molar ratios of 10-12 and subsequent heat treatment. Thermal behavior, phase composition, morphology and magnetic properties of samples were studied using DTA/TGA, XRD, SEM and VSM, respectively. Nano-crystalline Ba-hexaferrite with a mean crystallite size of 46 nm and magnetic properties as high as M s = 73.9 A.m 2 /kg and H ci = 334.2 kA/m was formed for mixture of 5.5Fe 2 O 3 +Ba(CH 3 COO) 2 which was milled for 48 h and then annealed at 1100 ºC.
Ceramics International, 2012
The effect of crystallinity and particle morphology of the submicron barium hexaferrite (BaFe 12 O 19) powders on the magnetic properties was investigated on powders synthesized by solid-state calcination (BHF-c) and molten salt synthesis (BHF-m) methods. Solid-state calcination route was found to yield agglomerated powders with poor crystallinity, whereas molten salt synthesis resulted in well crystallized powders with an anisometric morphology. The saturation magnetization of the BHF-m and BHF-c samples is 59 emu/g, and 56 emu/g at 300 K, and 90 emu/g, and 86 emu/g at 10 K. The temperature dependence of magnetization of the BHF-m is higher and the increase in magnetocrystal anisotropy with decreasing temperature is also steeper than that of the BHF-c due to the higher crystallinity. The magnetocrystalline anisotropy constant, K, calculated from the Stoner-Wohlfarth theory, of the BHF-m and BHF-c powders is 14.24 and 10.14 HA 2 /kg, respectively. The higher effective anisotropy, K eff of the BHFm is also confirmed through ferromagnetic resonance measurements. In conclusion, the higher crystallinity, slightly higher particle size and anisometric morphology of the BHF-m particles translated into higher magnetic properties and magnetocrystalline anisotropy.
Synthesis and characterization of barium hexaferrite nanoparticles
Journal of Materials Processing Technology, 2007
This investigation dealt with the synthesis of nanocrystalline barium hexaferrite (BaFe 12 O 19 ) powders through the co-precipitation-calcination route. The ferrite precursors were obtained from aqueous mixtures of barium and ferric chlorides by co-precipitation of barium and iron ions using 5 M sodium hydroxide solution at pH 10 in room temperature. These precursors were calcined at temperatures of 800-1200 • C for constant 2 h in a static air atmosphere. The effect of Fe 3+ /Ba 2+ mole ratio and addition of surface active agents during co-precipitation step on the structural and magnetic properties of produced ferrite powders were studied. It is found that the formation of single phase BaFe 12 O 19 powders was achieved by decreasing the Fe 3+ /Ba 2+ molar ratio from the stoichiometric value 12-8 and increasing the calcination temperature ≥1000 • C. In addition, the Fe 3+ /Ba 2+ mole ratio of 8 the surface active agents promoted the formation of homogeneous nanopowders (ca. 113 nm) of BaFe 12 O 19 at a low-temperature of 800 • C with resultant good magnetic saturations (50.02 emu/g) and wide intrinsic coercivities (642.4-4580 Oe).
Journal of Magnetism and Magnetic Materials, 1996
The combustion method, a fast and simple way of preparing sub-micrometer sized particles from a solution of the corresponding metal nitrates and a reducing agent (ODH, TFTA) which is used as a fuel, was adapted to the synthesis of barium hexaferrite particles. Structural and magnetic properties were investigated by X-ray diffraction, transmission electronic microscopy, magnetic measurements and M~ssbauer spectrometry on nanostructured as well as on microstructured particles resulting from annealing treatments under different conditions. High values of the coercive field (5.3 kOe) and of the magnetization (57.8 emu/g), at 13.5 kOe, were obtained on well crystallized BaFel2Oi9 particles annealed at 850°C.
2008
In recent years, the scientific efforts of a large number of research teams have been concentrating on developing, exploring and applying nanosized magnetic ferroxides. In this review, we consider the fundamental structural and magnetic characteristics of nanosized particles of barium hexaferrite. We discuss in some detail the most common techniques for preparation of nanosized ferroxide powders. Finally, we present original results on applying a promising chemical technique, namely, the single microemulsion technique, for the synthesis of barium hexaferrite powders consisting of homogeneous in shape and size particles.