Presentation Information
[P2-70]Hard magnetic and critical raw materials free permanent magnets on the basis of the Fe2P system
*Jürgen Gassmann1, Ruijuan Yan1, Iliya Radulov1, Oliver Diehl1, Fernando Maccari2, Konstantin Skokov2, Oliver Gutfleisch2 (1. Fraunhofer IWKS (Germany), 2. TU Darmstadt (Germany))
Keywords:
substitution,rare-earth free,gap-magnet,permanent magnet
Nowadays, high performance rare earth based permanent magnets like Nd-Fe-B and low performance ferrite magnets are the materials of choice for industrial applications. However, the quest for the successful synthesis of critical materials free hard magnets with superior magnetic properties is still ongoing. Materials desperately needed for a stable supply chain in the mobility and energy sectors, both crucial for reducing global carbon dioxide emissions.
As the most abundant and easily extractable 3d element, iron based rare earth free magnets have attracted much attention. Iron based compounds with some light elements such as boron, nitrogen, and phosphorous are ferromagnetic and have the potential to be used as permanent magnets. Among all these compounds, Fe2P is the most promising structure, due to a large magnetocrystalline anisotropy constant K1 (2.32 – 2.68 MJ/m³). However, reached coercivity in polycrystalline Fe2P-type magnets are so far from the empirical boundaries according to Brown’s paradox (0.65 T). Also, Curie temperature (Tc approx. 215 K) is rather low, due to weak ferromagnetism of Fe1 site in the crystal structure, another key property needing strong enhancement for industrial use of this material.
In this contribution, we present the synthesis of polycrystalline hard magnets with the Fe2P structure. First, a systematic study of single crystals is investigating magnetic and crystalline properties of phases in which the iron site is partially substituted by cobalt and nickel and the phosphorous side by silicon and aluminum. Second, polycrystalline samples are produced with optimal chemical composition derived from the single crystal study, by rapid-quenching techniques and subsequently ball milling. With this procedures, phase pure Fe2P type powder can be synthesized and compacted to dense magnets. So far, these magnets show rather low coercivity, which can be improved by grain boundary modification.
This work was partially supported by the Fraunhofer and Max Planck cooperation program, within the project MaRS – Critical materials lean magnets by recycling and substitution.
As the most abundant and easily extractable 3d element, iron based rare earth free magnets have attracted much attention. Iron based compounds with some light elements such as boron, nitrogen, and phosphorous are ferromagnetic and have the potential to be used as permanent magnets. Among all these compounds, Fe2P is the most promising structure, due to a large magnetocrystalline anisotropy constant K1 (2.32 – 2.68 MJ/m³). However, reached coercivity in polycrystalline Fe2P-type magnets are so far from the empirical boundaries according to Brown’s paradox (0.65 T). Also, Curie temperature (Tc approx. 215 K) is rather low, due to weak ferromagnetism of Fe1 site in the crystal structure, another key property needing strong enhancement for industrial use of this material.
In this contribution, we present the synthesis of polycrystalline hard magnets with the Fe2P structure. First, a systematic study of single crystals is investigating magnetic and crystalline properties of phases in which the iron site is partially substituted by cobalt and nickel and the phosphorous side by silicon and aluminum. Second, polycrystalline samples are produced with optimal chemical composition derived from the single crystal study, by rapid-quenching techniques and subsequently ball milling. With this procedures, phase pure Fe2P type powder can be synthesized and compacted to dense magnets. So far, these magnets show rather low coercivity, which can be improved by grain boundary modification.
This work was partially supported by the Fraunhofer and Max Planck cooperation program, within the project MaRS – Critical materials lean magnets by recycling and substitution.
