# Fileset

[REPM2025_O9-5_Luca.pdf](https://mdr.nims.go.jp/filesets/849e8db5-c17b-4eb5-8fcc-609ff716bbe8/download)

## Creator

Gabriel Gomez Eslava, Patricia de Rango, Sorana Luca

## Rights

[Creative Commons BY Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

## Other metadata

[Low temperature densification of Nd(Fe,Mo)12 nitrided samples](https://mdr.nims.go.jp/datasets/2f7d7bac-f915-4e78-8776-ea496b036c19)

## Fulltext

PowerPoint-Charte-CEA-2023Disposition : Titre imageLow temperature densification of Nd(Fe,Mo)12nitrided powdersGabriel Gomez Eslava1, Patricia de Rango2 and Sorana Luca11Univ. Grenoble Alpes, CEA, Liten, DTNM, 38000 Grenoble, France2Univ. Grenoble Alpes, CNRS, Institut Neel, 38000 Grenoble, FranceDisposition : Titre et contenu➢ NdFeB are strategic materials for our future society and especially for the green energy transition➢ E-mobility and wind turbines are expected to be the key driver of rare-earth permanent magnets demand growth over the future 2ContextS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Wood McKenzie Octobre. 2024To mitigate the risk of shortages and ensure future supplies in permanent magnets (PM) -> big challenges for our society:➢ Design of components to reduce the weight of PM➢ Reduce the waste of critical material by net shape process➢ Efficient recycling ➢ Searching RE-free or RE-lean permanent magnets capable to replace the benchmark NdFeB magnetsDisposition : Titre et contenu3ContextS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Searching RE-free or RE-lean permanent magnets capable to replace the benchmark NdFeB magnetsNew material should fulfil the following conditions:➢ Sufficient magnetic properties at room temperature and high temperatures → Magnetic hardness factor K = (µ0HA / 2Js)1/2 > 1➢ Allow an efficient economy of critical material = energy efficiency (RE economy vs available magnetic performances)30% RE economyK > 1 from RT up to 200°CRE-Fe12 7.7 at% REvsNd2Fe14B11.8 at% RES. Hirosawa, J. Magn. Soc. Jpn. 39 (2015) Disposition : Titre et contenu4Potential of the RE-Fe12 magnets compared to the NdFeB – Performance FactorS. Luca  - REPM 2025 Tsukuba  - 30/07/2025➢ Dense Sm-Fe12 based magnets have been recently reported in the literature, with coercivity as high as 1.5T and remanence of 0.71T (J.S. Zhang et al., Acta Mater. 2025)➢ Nd-Fe12 based compounds suffer from low magnetocristallineanisotropy at room temperature, that can be enhanced by the insertion of light atoms (N) into the 1-12 structure → densification of the nitrogenated powders proves to be difficult and up to now no dense Nd-Fe12 based magnet has been reported J.S.Zhang et al. – Acta Mater. 2025Sm-Fe12 based magnetDisposition : Titre et contenu5Potential of the RE-Fe12 magnets compared to the NdFeB – Performance FactorS. Luca  - REPM 2025 Tsukuba  - 30/07/2025➢ To evaluate the potential of these magnets in a system, compared to the NdFeB, the energy efficiency should be estimated ➢ Performance Factor (PF) = available magnetic performances (BHmax)/ RE content𝑷𝑭(𝒂𝒓𝒃.𝒖𝒏𝒊𝒕) =𝑩𝑯𝒎𝒂𝒙 ( Τ𝒌𝑱 𝒎𝟑)𝒙𝑹 (𝒘𝒕.%)𝐵𝐻𝑚𝑎𝑥 = ൗµ0𝑀𝑟24𝑀𝑟 = 0,9 ∗ 𝑀𝑠Here xR = RE % wtWhen values of BHmax and Mr are not measured, they are estimatedusing the formulas below:Disposition : Titre et contenu6Potential of the RE-Fe12 magnets compared to the NdFeB – Performance FactorS. Luca  - REPM 2025 Tsukuba  - 30/07/2025 The potential of the Sm-Fe12 based magnets is hindered by the low remanence values → the challenge is to enhance the Br values Great potential of the Nd(Fe,Mo)12N based magnets for PM applications for temperatures up to 180°C (economy of approximately 10% of RE for the same BHmax) without using HRE elements However, the densification of the nitrogenated powders is the biggest challengeµ0Ms (T)µ0Mr=0.9 µ0Ms(T)PFTemp. (°C) 25 180 25 180 25 180N50 NdFeB 1.6 1.3 1.42 1.15 13.3 10.8NdFe10.5Mo1.5N [1] 1.1 0.9 1* 0.81* 14.6 12.0Sm8Fe73.5Ti8V8Al2Cu0.5 [2] 0.74 0,42 0.62 0.45 9.6 6.9Sm8Fe76.5Ti5V8Al2Cu0.5 [3] 0.81 - 0.71 10.9[1] S. Luca et al., JALCOM 2025[2] A. Srinithi et al., Acta Mater. 2023[3] J.S.Zhang et al., Acta Mater. 2025 *Represents calculated values using:Mr= 0,9 ∗ 𝑀𝑠 and Ms = measured value𝑷𝑭(𝒂𝒓𝒃.𝒖𝒏𝒊𝒕) =𝑩𝑯𝒎𝒂𝒙 ( Τ𝒌𝑱 𝒎𝟑)𝒙𝑹 (𝒘𝒕.%)𝐵𝐻𝑚𝑎𝑥 = ൗµ0𝑀𝑟24Disposition : Titre et contenu7Densification of the Nd(Fe,Mo)12N powdersS. Luca  - REPM 2025 Tsukuba  - 30/07/2025➢ Nd(Fe,Mo)12N powders are not stable at high temperatures (> 600°C) → conventional sintering cannot be applied➢ Low melting temperature phase at grain boundaries can assist the densification at low temperatures 98% of NdFe10,5Mo1,5 phase2%   of Nd + Nd-O phases 200 400 600 800Temperature (°C)DSC/heat flow (a.u.)Endothermic480°C➢ Presence of the RE-Cu eutectic➢ Nitrogenated powders have: HA = 11T, Ms = 1.1T, TC = 300°C➢ Elaboration of (Nd,Pr)1.35Fe10.5Mo1.5Cu0.1 alloy by SC – almost single 1-12 phaseDisposition : Titre et contenu➢ Fine microstructure with grains of 100 to 1000 nm➢ Cu is present predominantly at triple points together with RE elements➢ Well defined RE-Cu phase cannot be observed at GBs → difficult to promote the liquid phase sintering assisted by the low melting eutectic880 nm80 nm 80 nm80 nm 80 nm50 nmS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Densification of the Nd(Fe,Mo)12N powdersS. Luca et al., JALCOM (2024) Nd Pr CuFe Mo OSC ribbonDisposition : Titre et contenu➢ Combination of high temperature + low temperature annealing treatment → better wettability of the RE-Cu phase at grain boundaries➢ However, high temperature annealing also induces grain growth → detrimental for coercivity development 980 nm80 nm 80 nm80 nm 80 nm50 nmS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Densification of the Nd(Fe,Mo)12N powdersSC ribbonDisposition : Titre et contenu1080 nm80 nm 80 nm80 nm 80 nm50 nmS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Densification of the Nd(Fe,Mo)12N powdersOur approach:➢ Spark Plasma Sintering (SPS): allows to densify the powders by simultaneous application of a pressure + temperature, in a closed system under vacuum or N2 or Ar gas ➢ Two powder blending – assists the densification at low temperatures  Search for low melting temperature compoundsfulfilling the following conditions:o Melting temperature < 600°Co The constituents are not soluble into the 1-12 phase o Paramagnetic phase -> allow to develop the coercivityDisposition : Titre et contenu1180 nm80 nm 80 nm80 nm 80 nm50 nmS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Densification of the Nd(Fe,Mo)12N powdersOur approach: Search for low melting temperature compounds fulfilling the following conditions:o Melting temperature < 600°Co The constituents are not soluble into the 1-12 phase o Paramagnetic phase -> allow to develop the coercivity➢ La – does not form stable 1-12phase➢ Cu, Zn – do not stabilize the 1-12 structure➢ hard to manipulate (highoxidation risk)Cu16La84 wt.%Zn14La86 wt.%H. Okamoto, Journal of Phase Equilibria (2001, 2011)Tmelt = 475°C Tmelt = 523°CDisposition : Titre et contenu1280 nm80 nm 80 nm80 nm 80 nm50 nmS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Densification of the Nd(Fe,Mo)12N powdersOur approach: Search for low melting temperature compounds fulfilling the following conditions:o Melting temperature < 600°Co The constituents are not soluble into the 1-12 phase o Paramagnetic phase -> allow to develop the coercivity➢ Al, Ga can stabilize the 1-12 structure➢ Cu – do not stabilize the 1-12 structure➢ easier to manipulateCu16La84 wt.%Zn14La86 wt.%Cu67Al33 wt.%Ga rich Al-GaTmelt = 548.2°C liq > 200°CDisposition : Titre et contenu1380 nm80 nm 80 nm80 nm 80 nm50 nmS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Densification of the Nd(Fe,Mo)12N powdersPhase SpaceGroupLattice parameters(nm)%Al2Cu I 4/m c m a=b=6.066 c=4.880 54Al F m 3 m a=4.047 46 Cu Al OCu Al O➢ Al67Cu33 alloy fabricated by melting the pure elements in an induction furnace Disposition : Titre et contenu1480 nm80 nm 80 nm80 nm 80 nm50 nmS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Densification of the Nd(Fe,Mo)12N powdersLow melting point alloy (pieces or powder).Test of the ability of the eutectic alloy to form GB phases – infiltration experiment on a SC ribbon Annealed Nd(FeMo)12 flakes with optimized µ-structureRE-Al-Cu rich phase with low Fe contentCu Al Fe MoNd PrAl-CuSC ribbonLow temperature heat treatment (< 600°C)Low melting point alloy (pieces or powder).Test of the ability of the eutectic alloy to form GB phases – infiltration experiment on a SC ribbon Annealed Nd(FeMo)12 flakes with optimized µ-structureDisposition : Titre et contenu1580 nm80 nm 80 nm80 nm50 nmS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Densification of the Nd(Fe,Mo)12N powdersSEM image analysis ➔ grains / GB = 80/20 % vol75% vol. of jet mill Nd(Fe,Mo)12Cu0.1Nx + 25% vol. mechanical milled AlCu➢ T = 560°C, under 600 MPa➢ Measured density = 6,69 g/cm3 representing 94.8% of the theoretical densityDisposition : Titre et contenu1680 nm80 nm 80 nm80 nm50 nmS. Luca  - REPM 2025 Tsukuba  - 30/07/2025Densification of the Nd(Fe,Mo)12N powders➢ Grains of nitrogenated 1-12 phase are separated by Al-Cu phase, which is spread out around the magnetic grains → it seems that the low melting eutectic assisted the densification of the nitrogenated powders1-12 grainAl-CuNd Fe MoAl Cu NDisposition : Titre et contenu➢ The RE-Fe12 compounds are verry promising material for next generation PM➢ Nd(Fe,Mo)12Cu compound has a great potential for future permanent magnet➢ High magnetocristalline anisotropy (11T)➢ High saturation magnetization (1.1T)➢ Moderate Curie temperature (300°C) ➢ The big challenge is to densify the nitrogenated powders under the decomposition temperature of the nitride (< 600°C)➢ Powder blend method + SPS have been applied in order to densify the powders at 560°C ➔ density of 95%, without the decomposition of the nitride ➢ Fe-lean RE-Al-Cu-rich grain boundaries are formed with an appropriate thermal treatment that can be beneficial for coercivity development17Conclusion S. Luca  - REPM 2025 Tsukuba  - 30/07/2025Next challenge: develop the coercive microstructure formed of fine 1-12 grains + non-magnetic grain boundariesDisposition : FINMerciCEA Liten38229 Grenoble CedexFrancesorana.luca@cea.frありがとうThank youmailto:sorana.luca@cea.fr