Exploiting different morphologies of non-ferromagnetic interacting precursor’s for preparation of hexaferrite magnets

Vijayan, Harikrishnan; Povlsen, Amalie; Thomas-Hunt, Jack; Mørch, Mathias; Christensen, Mogens

doi:10.1016/j.jallcom.2022.165333

Cited by 8 publications

(17 citation statements)

References 48 publications

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Section: Resultsmentioning

confidence: 99%

“…The method has earlier been reported as a simple, easy, and green solution to prepare and create texture in MHF. 20,21 The samples have been investigated using in-house powder X-ray diffraction (PXRD) and transmission synchrotron diffraction. Synchrotron measurements by multiple sample orientations was treated using the Material Analysis Using Diffraction (MAUD)-software, 22 which allowed for a full texture analysis using the E-WIMV model.…”

Section: Papermentioning

confidence: 99%

“…This is also seen for aligned samples of MHF, where non-magnetic and anisotropic-shaped crystallites of goethite and sixline-ferrihydrite result in high texture indices and high M r /M s . 20,21,43 Table 3 list the comparison of M r /M s to texture indices for aligned hard M-type hexaferrites magnets found within the existing literature. In general, it is clear that higher texture indices correspond to higher M r /M s values, however the sample presented with the highest texture index is not the sample with the highest M r /M s value.…”

Section: Paper Dalton Transactionsmentioning

confidence: 99%

“…7 Texture index related to M r /M s for differently prepared samples of hard M-type hexaferrites found in the literature. 11,20,21,43,[45][46][47][48] Specific details such as synthesis condition, pressing technique and texture model are presented for some of the samples in Table 3.…”

Section: Conflicts Of Interestmentioning

confidence: 99%

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Texture formation in W-type hexaferrite by cold compaction of non-magnetic interacting anisotropic shaped precursor crystallites

2023

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Section: Resultsmentioning

confidence: 99%

Section: Papermentioning

confidence: 99%

Section: Paper Dalton Transactionsmentioning

confidence: 99%

Section: Conflicts Of Interestmentioning

confidence: 99%

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Texture formation in W-type hexaferrite by cold compaction of non-magnetic interacting anisotropic shaped precursor crystallites

2023

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“…Previously we have reported on strontium hexaferrites synthesized from various nonmagnetic precursors like six-line ferrihydrite, hematite (α-Fe 2 O 3 ), and goethite (α-FeOOH). − However, the low sintering temperatures resulted in poor sample densities and increasing the temperature caused low H c due to excessive crystallite grain growth. One of the key balances in hexaferrite ceramics comes from the fact that massive grain growth, which damages coercivity, occurs at the temperatures required for obtaining densities above 90% of the theoretical density. , …”

Section: Introductionmentioning

confidence: 99%

High-Performance Hexaferrite Ceramic Magnets Made from Nanoplatelets of Ferrihydrite by High-Temperature Calcination for Permanent Magnet Applications

Vijayan

Laursen

Stingaciu

et al. 2023

ACS Appl. Nano Mater.

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Highly aligned ceramic hexaferrite magnets with high-energy products (BH) max and a density exceeding 90% of theoretical density have been fabricated. The precursors were an antiferromagnetic powder, a six-line ferrihydrite mixed with SrCO 3 , and a grain growth inhibitor SiO 2 . Conventional cold compaction of the precursor powders was employed prior to calcination at temperatures of 1050, 1150, and 1250 °C. The influence of calcination temperature and magnetic properties has been systematically studied in the produced ceramic magnets. Conventional cold compaction is a favorable route for industrial production when compared with other compaction techniques like spark plasma sintering, hot compaction, or electroforging. A high (BH) max of 25.2 kJ/m 3 was obtained for the best magnet along with an appreciable coercivity, H c , of 187 kA m −1 , a high squareness ratio, M r /M s , of 0.84, and a saturation magnetization, M s , of 73 A m 2 /kg. Texture and crystallite size analysis were extracted from 2D synchrotron transmission powder diffraction measurements. We have demonstrated that high-performance bulk magnets for permanent magnet applications can be produced from nonmagnetic interacting crystallites mixed with a grain growth inhibitor without applying a magnetic field for alignment.

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Aligned Permanent Magnet Made in Seconds–An In Situ Diffraction Study

Laursen,

Frandsen,

Shyam

et al. 2024

Adv Elect Materials

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The synthesis of a strontium hexaferrite magnet is studied using in situ synchrotron powder X‐ray diffraction (PXRD) with a 16‐ms time resolution. The precursor material is cold compacted shape‐controlled goethite and strontium carbonate. The time evolution of the phases is modeled with sequential Rietveld refinements revealing that strontium hexaferrite forms within seconds at ≈1173 K. Texture analysis is performed on selected PXRD frames throughout the experiment, and the preferred orientation introduced by cold‐pressing goethite prevails through the iron oxide phase transitions (goethite → hematite → strontium hexaferrite). Electron backscatter diffraction (EBSD) data on the final pellet confirms the preferred orientation observed with PXRD. The resulting magnet has respectable magnetic properties, considering the simplicity of the preparation method, with an energy product (BHmax) of 18.6(8) kJ m−3.

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Exploiting different morphologies of non-ferromagnetic interacting precursor’s for preparation of hexaferrite magnets

Cited by 8 publications

References 48 publications

Texture formation in W-type hexaferrite by cold compaction of non-magnetic interacting anisotropic shaped precursor crystallites

Texture formation in W-type hexaferrite by cold compaction of non-magnetic interacting anisotropic shaped precursor crystallites

High-Performance Hexaferrite Ceramic Magnets Made from Nanoplatelets of Ferrihydrite by High-Temperature Calcination for Permanent Magnet Applications

Aligned Permanent Magnet Made in Seconds–An In Situ Diffraction Study

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