(Fe,Co)2(P,Si) rare-earth free permanent magnets: From macroscopic single crystals to submicron-sized particles

Yibole, H.; Lingling-Bao,; Xu, Jun; Alata, Hexig; Tegus, O.; Hanggai, W.; Dijk, N.H. van; Brück, E.; Guillou, F.

doi:10.1016/j.actamat.2021.117388

Cited by 7 publications

(15 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From a quantitative point of view, the present samples prepared using short sintering show tenfold larger coercivities ( H C ≈ 0.58 kOe) than that found in bulk polycrystalline samples sintered for 24 h ( H C typically less than 50 Oe) or single crystals ( H C typically less than 20 Oe) [ 26 , 29 , 30 ]. However, the coercivities are twice as small as that observed in sub-micron-sized (Fe,Co) 2 (P,Si) particles obtained by ball milling (ball-milling stage after a solid-state synthesis, H C up to approximately 1.4 kOe at room temperature [ 29 ]).…”

Section: Resultsmentioning

confidence: 93%

“…While further insights into the coercivity mechanism would be needed to ascertain it, we may nonetheless point out that the structural and magnetic inhomogeneities due to secondary phases impeding the domain wall motion could well be responsible for observing the largest coercivities in the samples with large amounts of Fe 3 P and/or Fe 3 Si secondary phases. In addition, former studies in (Fe,Co) 2 P ternary compounds observed a coercivity optimum for the Co content corresponding to the Fe 2 P-type/Co 2 P-type structural boundary [ 17 , 18 ], and in sub-micron-sized (Fe,Co) 1.95 (P,Si) particles the largest coercivity was observed in a sample presenting a two-phase mixture of Fe 2 P-type and orthorhombic BCO-type structures [ 29 ]. These observations could also be in line with a pinning-type coercivity favored by structural disorder and large secondary-phase contents.…”

Section: Resultsmentioning

confidence: 99%

“…Recent experimental studies in bulk (Fe,Co) 2 (P,Si) polycrystalline materials have indeed shown that simultaneous metal and metalloid substitutions can raise the Curie temperature ( T C up to 650 K) while maintaining a relatively large c -axis uniaxial magnetocrystalline anisotropy and the desired hexagonal Fe 2 P-type structure [ 26 , 27 , 28 ]. Single-crystal studies have confirmed the combination of significant room-temperature anisotropy ( K 1 in the range 0.9 to 1.1 MJ m −3 ), sizable saturation magnetization (corresponding to saturation polarization of 0.8–1.0 T at room temperature) and high Curie temperatures, making (Fe,Co) 2 (P,Si) quaternary alloys intrinsically promising for permanent magnet applications [ 29 , 30 ]. Unfortunately, neither (Fe,Co) 2 (P,Si) bulk polycrystalline materials nor single crystals present a noticeable magnetic coercivity at room temperature.…”

Section: Introductionmentioning

confidence: 99%

“…In (Fe,Co) 2 P ternary compounds, a shaping into fine or ultrafine particles at the synthesis stage by Cu lixiviating or plasma atomization was found suitable to induce coercivity [ 17 , 18 ]. Similarly, high-energy ball milling of (Fe,Co) 2 (P,Si) bulk polycrystalline samples into submicron sized particles after the sintering stage was reported to induce a coercivity of H C ≈ 1.4 kOe [ 29 ]. However, this post-sintering ball-milling approach is not ideal.…”

Section: Introductionmentioning

confidence: 99%

“…However, this post-sintering ball-milling approach is not ideal. It is a lengthy process that is difficult to upscale and the coercivity remains particularly low compared to the anisotropy field ( H a ), with a coercive field over anisotropy field ratio of, typically, H C / H a ~3% [ 29 ]. One should seek alternative methods to prepare (Fe,Co) 2 (P,Si) samples while ensuring a microstructure compatible with hard properties.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Optimizing the Sintering Conditions of (Fe,Co)1.95(P,Si) Compounds for Permanent Magnet Applications

Yiderigu,

Yibole,

Bao

et al. 2024

Materials

Self Cite

View full text Add to dashboard Cite

(Fe,Co)2(P,Si) quaternary compounds combine large uniaxial magnetocrystalline anisotropy, significant saturation magnetization and tunable Curie temperature, making them attractive for permanent magnet applications. Single crystals or conventionally prepared bulk polycrystalline (Fe,Co)2(P,Si) samples do not, however, show a significant coercivity. Here, after a ball-milling stage of elemental precursors, we optimize the sintering temperature and duration during the solid-state synthesis of bulk Fe1.85Co0.1P0.8Si0.2 compounds so as to obtain coercivity in bulk samples. We pay special attention to shortening the heat treatment in order to limit grain growth. Powder X-ray diffraction experiments demonstrate that a sintering of a few minutes is sufficient to form the desired Fe2P-type hexagonal structure with limited secondary-phase content (~5 wt.%). Coercivity is achieved in bulk Fe1.85Co0.1P0.8Si0.2 quaternary compounds by shortening the heat treatment. Surprisingly, the largest coercivities are observed in the samples presenting large amounts of secondary-phase content (>5 wt.%). In addition to the shape of the virgin magnetization curve, this may indicate a dominant wall-pining coercivity mechanism. Despite a tenfold improvement of the coercive fields for bulk samples, the achieved performances remain modest (HC ≈ 0.6 kOe at room temperature). These results nonetheless establish a benchmark for future developments of (Fe,Co)2(P,Si) compounds as permanent magnets.

show abstract