Enhancement of magnetic properties by spark plasma sintering of hydrothermally synthesised SrFe<sub>12</sub>O<sub>19</sub>

Eikeland, Anna Zink; Stingaciu, Marian; Granados-Miralles, Cecilia; Saura-Múzquiz, Matilde; Andersen, Henrik L.; Christensen, Mogens

doi:10.1039/c6ce02275h

Cited by 23 publications

(39 citation statements)

References 30 publications

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“…The data reveal the SPS_MSG pellets to be significantly better aligned than SPS_CSG. Previous studies of SPS compaction have been reported for pellets made from SrFe 12 O 19 platelet crystallites synthesised by hydrothermal methods 21 , 27 . In both studies, the powder samples used for SPS compaction are characterised by being hexagonal platelet-like particles with large AB/C aspect ratios.…”

Section: Resultsmentioning

confidence: 99%

“…However, one of the main challenges is that the crystallites are partly intergrown into one-another, making them unsusceptible to alignment using pressure or applied magnetic field. Highly aligned crystallites have been reported to significantly improve the magnetic performance of compacted nanopowders 20 , 21 , and the nanocrystallites ability to freely rotate and align is essential for reaching a high energy product. Sapoletova et al .…”

Section: Introductionmentioning

confidence: 99%

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Enhancement of magnetic properties through morphology control of SrFe12O19 nanocrystallites

Eikeland

Stingaciu

Mamakhel

et al. 2018

Sci Rep

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Nanocrystallites of the permanent magnetic material SrFe12O19 were synthesised using a conventional sol-gel (CSG) and a modified sol-gel (MSG) synthesis route. In the MSG synthesis, crystallite growth takes place in a solid NaCl matrix, resulting in freestanding nanocrystallites, as opposed to the CSG synthesis, where the produced nanocrystals are strongly intergrown. The resulting nanocrystallites from both methods exhibit similar intrinsic magnetic properties, but significantly different morphology and degree of aggregation. The nanocrystallites were compacted into dense pellets using a Spark Plasma Sintering (SPS) press, this allows investigating the influence of crystallite morphology and the alignment of the nanocrystallites on the magnetic performance. A remarkable correlation was observed between the crystallites morphology and their ability to align in the compaction process. Consequently, a significant enhancement of the maximum energy product was obtained after SPS for the MSG prepared sample (22.0 kJ/m3), compared to CSG sample, which achieved an energy product of 11.6 kJ/m3.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhancement of magnetic properties through morphology control of SrFe12O19 nanocrystallites

Eikeland

Stingaciu

Mamakhel

et al. 2018

Sci Rep

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“…This value is about 25% larger than achieved for MHFs. Toyota (1997) also reported a BH max of 42 kJ m À3 for SrFe 18 O 27 , which is significantly higher than for pure SrFe 12 O 19 , normally limited to about 30 kJ m À3 (Eclipse Magnetics Ltd, 2019; Eikeland et al, 2017). Furthermore, WHFs have also revealed themselves as promising materials for other applications, e.g.…”

Section: +mentioning

confidence: 99%

“…Although not as powerful as Nd 2 Fe 14 B magnets, ferrites are the most abundantly used permanent magnetic material throughout the world as a result of their low cost, high stability and adequate performance in many applications (Pullar, 2012; Lewis & Jimé nez-Villacorta, 2013). Recent work has focused on optimizing the performance of MHFs through bottom-up nanostructuring and morphology control (Eikeland et al, 2018(Eikeland et al, , 2017Saura-Muzquiz et al, 2016. However, there is still a huge gap in performance between REE magnets and REE-free magnets (Coey, 2012), encouraging further research into REE-free magnets.…”

Section: Introductionmentioning

confidence: 99%

Structure and magnetic properties of W-type hexaferrites

Mørch

Ahlburg

Saura-Múzquiz

et al. 2019

IUCrJ

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W-type hexaferrites (WHFs) (SrMe 2Fe16O27, Me = Mg, Co, Ni and Zn) are hard magnetic materials with high potential for permanent magnet applications owing to their large crystalline anisotropy and high cation tunability. However, little is known with regards to their complex structural and magnetic characteristics. Here, the substitution of metals (Me = Mg, Co, Ni and Zn) in WHFs is described and their crystal and magnetic structures investigated. From joined refinements of X-ray and neutron powder diffraction data, the atomic positions of the Me atoms were extracted along with the magnetic dipolar moment of the individual sites. The four types of WHFs exhibit ferrimagnetic ordering. For Mg, Ni and Zn the magnetic moments are found to be ordered colinearly and with the magnetic easy axis along the crystallographic c axis. In SrCo2Fe16O27, however, the spontaneous magnetization changes from uniaxial to planar, with the moments aligning in the crystallographic ab plane. Macromagnetic properties were measured using a vibration sample magnetometer. The measured saturation magnetization (M s) between the different samples follows the same trend as the calculated M s extracted from the refined magnetic moments of the neutron powder diffraction data. Given the correlation between the calculated M s and the refined substitution degree of the different Me in specific crystallographic sites, the agreement between the measured and calculated M s values consolidates the robustness of the structural and magnetic Rietveld model.

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“…The synthesis of CoFe 2 O 4 followed the steps reported in the literature (Andersen et al, 2019;Eikeland et al, 2017;Stingaciu et al, 2017;Andersen & Christensen, 2015). In short, a stoichiometric 1:2 molar ratio of Co:Fe was mixed directly in a Teflon-lined steel autoclave using aqueous solutions of 3.0 M research papers Co(NO 3 ) 2 Á6H 2 O and 2.3 M Fe(NO 3 ) 3 Á9H 2 O (reagent grade, Sigma-Aldrich).…”

Section: Synthesis Of Cofe 2 O 4 Nanopowdersmentioning

confidence: 99%

Air-heated solid–gas reaction setup for in situ neutron powder diffraction

Ahlburg

Canévet²,

Christensen

2019

J Appl Cryst

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The design and function of a reduction furnace, specially designed for solid-gas in situ monochromatic angular dispersive neutron powder diffraction, is presented. The functionality is demonstrated by performing a reduction experiment of CoFe 2 O 4 nanoparticles at the instrument DMC at SINQ. Heating is provided by an air gun, allowing the sample to reach temperatures in the range of 300-973 K within less than 5 min. The setup is based on a single-crystal sapphire tube with one end closed. A ' scan of the tube reveals its single-crystal nature, through strong single-crystal reflections, while the remaining background is very low, uniform and flat. CoFe 2 O 4 was reduced using a time resolution of 8 min and a sample volume of $2 cm 3 . By means of sequential Rietveld refinement of the in situ neutron diffraction data, a two-step reduction mechanism was discovered: CoFe 2 O 4 ! Co 0.33 Fe 0.67 O ! CoFe 2 . The setup offers high temperatures, fast temperature stability, large sample volumes and respectable time resolution. The setup has proven to be ideal to carry out investigations of advanced materials under realistic conditions. The ability to investigate real materials in real time under realistic conditions may be a significant advantage for scientific investigations as well as for industrial applications.

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Enhancement of magnetic properties by spark plasma sintering of hydrothermally synthesised SrFe₁₂O₁₉

Cited by 23 publications

References 30 publications

Enhancement of magnetic properties through morphology control of SrFe12O19 nanocrystallites

Enhancement of magnetic properties through morphology control of SrFe12O19 nanocrystallites

Structure and magnetic properties of W-type hexaferrites

Air-heated solid–gas reaction setup for in situ neutron powder diffraction

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Enhancement of magnetic properties by spark plasma sintering of hydrothermally synthesised SrFe12O19

Cited by 23 publications

References 30 publications

Enhancement of magnetic properties through morphology control of SrFe12O19 nanocrystallites

Enhancement of magnetic properties through morphology control of SrFe12O19 nanocrystallites

Structure and magnetic properties of W-type hexaferrites

Air-heated solid–gas reaction setup for in situ neutron powder diffraction

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Enhancement of magnetic properties by spark plasma sintering of hydrothermally synthesised SrFe₁₂O₁₉