# Fileset

[REPM2025_O16-2_Zhang.pdf](https://mdr.nims.go.jp/filesets/f9f7ae79-8be6-4417-8912-59e6ec12445d/download)

## Creator

Xinyi Ji, Lanting Zhang, Hong Zhu, Zhaozhe Zhong, Jian Liu, Zhanji Dong, Zhongjie Peng, Kaihong Ding

## Rights

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

## Other metadata

[Accelerated development of thermally stable Nd-Fe-B magnets with light rare-earth elements and their synergetic effects to temperature stability with Co](https://mdr.nims.go.jp/datasets/1afc26ef-f6cf-41ea-aa4e-44997b06b533)

## Fulltext

Investigation on the structure, chemistry and magnetism of R2Fe14B-type compounds材料科学与工程学院School of Materials Science and Engineering1896 1935 1987 2006Accelerated development of thermally stable Nd-Fe-B magnets with light rare-earth elements and their synergetic effects to temperature stability with CoXinyi Ji1, Lanting Zhang1, Hong Zhu2, Zhaozhe Zhong3, Jian Liu3, Zhanji Dong4, Zhongjie Peng4, Kaihong Ding41. School of Materials Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China2. University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China3. Advanced Engineering Research Division, Toyota Motor Technical Research and Service (Shanghai) Co., Ltd, 6333 North Jiasong Road, Shanghai 201804, China4. Yantai Dongxing Magnetic Materials Inc., 888 Yongda Street, Yantai 265500, China[O16-2]材料科学与工程学院School of Materials Science and EngineeringBackground Thermal stabilityCostActa Materialia, 158 (2018) 118-137, https://doi.org/10.1016/j.actamat.2018.07.049~150CPerform/cost is an everlasting topic in engineering.HEV/EVWind turbineRobot2https://doi.org/10.1016/j.actamat.2018.07.049材料科学与工程学院School of Materials Science and EngineeringAttempts on Nd-Fe-B-based magnets3JALCOM, 790(2019) 750-759Scripta Materialia, 67(2012) 530Materials & Design 209 (2021) 1100042. Grain boundary phase modification1. Grain size refinement3. Grain boundary diffusion process 4. Cost-effective magnets w. high abundance REJ. Chn Soc. Rare Earths 41 (2023) 79材料科学与工程学院School of Materials Science and EngineeringThe purpose of this work• To explore magnets with exceptional high temperature stability at ~150℃ and above.• Use cost-effective LREs for the performance cost of magnet instead of using HREs, high-Tc elements.• Development under the near mass-production condition.4RE=NdPr, La, Ce, YTM=Fe, Co, Ni,[(Nd0.8Pr0.2)(1-x)(La/Ce/Y)x]13.86[Fe(1-y)(Co/Ni)y]77.10M3.30B5.74 (M=Al, Cu, Ga, Ti), at.% 材料科学与工程学院School of Materials Science and EngineeringMagnetic properties of the 24 starting compos.51. For Br@150C, higher values than that of pristine Nd–Fe–B could be achieved at a high doping level of Co. 2. A decrease in Hcj is observed for all the doping species except Ni.J. Mater. Chem. A, 2023, 11, 8988材料科学与工程学院School of Materials Science and EngineeringPhase constitution and microstructure of the magnets6微观结构10 μmNdOxNd6Fe13GaCeFe25 μmNdCo3NdOx2:14:1 phase >95% MicrostructureGrain size: 4~5 m材料科学与工程学院School of Materials Science and EngineeringPhase constitution and microstructure of the magnets7Details at GB in a La0.25Co0.25 magnetPartitioning behavior:Main phase wt.%Nominal wt.%La: 0.57Ce: 0.76 Y: 0.94Ni: 0.68 Co: 0.98材料科学与工程学院School of Materials Science and EngineeringThe adaptive-learning framework 8J. Mater. Chem. A, 2023, 11, 89881. Kick-start model: constructing a rough initial surrogate model with a very small amount of data24 starting compos.4. Experimental feedback to update the surrogate model2. Bayesian Optimization (BO) to make recommendations to max. optimal candidate3. Magnets prepared in the company材料科学与工程学院School of Materials Science and EngineeringModel construction91. 16 atomic features 2. Feature engineering3. Uncertainty estimation: booststrapping4. Acquisition function: upper confidence bound材料科学与工程学院School of Materials Science and EngineeringStage 1 optimization:  Br@150°C• To identify compositions with exceptional HT Br10La/Co/Ni combination is recommendedThe performance is highly related to costHowever, this is also accompanied by a general decrease in Hcj@150°C材料科学与工程学院School of Materials Science and EngineeringStage 2 optimization:  Br@80°C*Hcj@150°C• To improve the overall performance11Performance–cost ratio: GBr&Hcj = MBr&Hcj /cost The best two candidates showed 18.4% (3: C1) and 13.1% (3: C2) improvement in performance-cost ratio with respect to benchmark Nd-Fe-BImproved performance-cost ratio材料科学与工程学院School of Materials Science and EngineeringEvolution of properties after iteration12• After 4 rounds of iteration, composition with higher performance to the base composition but 10% lower cost was found. 0 1 2 3 40102030405060Br@20℃*Hcj@150℃IterationBase magnetCe3.31Y0.27Co0.26Ni0.37（cost -10%）• The La-Co, Ce-Co, La-Co-Ni combinations outperform the other combinations. 材料科学与工程学院School of Materials Science and EngineeringThe La-Co pairs w/. higher Mr above 150C13[(Nd0.8Pr0.2)(1-x)(La/Ce)x]13.86[Fe(1-y)Coy]77.10TM3.30B5.74 (0≤x≤0.25, 0≤y≤0.25, TM=Al, Ti, Cu, Ga), at.%Benchmark BenchmarkBoth the Mr of the La0.25Co0.125and La0.25Co0.25 magnets outperform the undoped and Ce-doped ones above 150C. 材料科学与工程学院School of Materials Science and EngineeringEffect of LRE-Co pair on T stability of Mr14• Without Co, the Mr@180C of La-doped magnet is inferior to that of Ce-doped one• For La0.25Co0.125, higher Mr@180C despite its lower Tc than Ce0.25Co0.25• The La0.25Co0.25 and Ce0.25Co0.25 magnets demonstrate almost the same α as that of the Co0.25 even though much lower TcCo dopedCe-Co dopedLa-Co dopedCo dopedCe-Co dopedLa-Co dopedCurie temperature Mr@180C 𝛼 𝑇 =𝜇0𝑀𝑟 180℃ − 𝜇0𝑀𝑟 20℃𝜇0𝑀𝑟 20℃ × ∆𝑇材料科学与工程学院School of Materials Science and EngineeringPreferential site occupation of La• La0.25Co0.25, La preferentially occupies the 4g-site15Zone axis 4g-site 4f-site[110] 9.55±0.54 7.34±0.51[100] 6.91±0.26 5.69±0.23La concentration (at.%)材料科学与工程学院School of Materials Science and EngineeringPreferential site occupation of Ce• Ce0.25Co0.25• Ce preferentially occupies the 4f-site16Zone axis 4g-site 4f-site[110] 4.70±0.25 6.39±0.32Ce concentration (at.%)材料科学与工程学院School of Materials Science and EngineeringPreferential site occupations of Co17Mössbauer spectraFe site Undoped Co0.25La0.25Co0.125La0.25Co0.25Ce0.25Co0.2516k1 28.57 21.09 12.86 12.12 26.4216k2 28.57 18.88 25.28 24.24 20.858j1 14.29 24.18 18.96 24.15 11.958j2 14.29 11.11 12.77 13.15 16.204c 7.14 7.85 19.5 8.37 14.194e 7.14 16.9 10.61 17.98 10.39Pref. occup.16k1,16k2, 8j216k1 16k1 8j1Refined relative areas (±1%) of the Fe sites in the lattice• Preferential occupations of the 16k1, 16k2 and 8j2 sites by Co alone• If with La, Co occupies the 16k1 site preferentially• If with Ce, Co occupies the 8j1 site preferentially材料科学与工程学院School of Materials Science and EngineeringSummary• Several promising compositions with La, Ce, Y, Co and Ni as doping elements with good HT remanence and/or enhanced performance-cost ratio are identified through BO approach, which could impact the development of novel magnet for HT application.• La-Co pair shows the good HT remanence (>150C) over the pristine magnet and Ce-Co pair, possibly due to the specific site occupation of the elements in the lattice.18材料科学与工程学院School of Materials Science and EngineeringTHANK YOU FOR YOUR ATTENTION!19 幻灯片 1: Accelerated development of thermally stable Nd-Fe-B magnets with light rare-earth elements and their synergetic effects to temperature stability with Co 幻灯片 2: Background  幻灯片 3: Attempts on Nd-Fe-B-based magnets 幻灯片 4: The purpose of this work 幻灯片 5: Magnetic properties of the 24 starting compos. 幻灯片 6: Phase constitution and microstructure of the magnets 幻灯片 7: Phase constitution and microstructure of the magnets 幻灯片 8: The adaptive-learning framework  幻灯片 9: Model construction 幻灯片 10: Stage 1 optimization:  Br@150°C 幻灯片 11: Stage 2 optimization:  Br@80°C*Hcj@150°C 幻灯片 12: Evolution of properties after iteration 幻灯片 13: The La-Co pairs w/. higher Mr above 150C 幻灯片 14: Effect of LRE-Co pair on T stability of Mr 幻灯片 15: Preferential site occupation of La 幻灯片 16: Preferential site occupation of Ce 幻灯片 17: Preferential site occupations of Co 幻灯片 18: Summary 幻灯片 19: Thank you for your attention!