Application of HoH2 hydride for improving the hysteretic properties of Pr-Fe-B magnets at low temperatures

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61989100%3A27360%2F18%3A10241408" target="_blank" >RIV/61989100:27360/18:10241408 - isvavai.cz</a>

Result on the web

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DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Application of HoH2 hydride for improving the hysteretic properties of Pr-Fe-B magnets at low temperatures

Original language description

Currently, processes named as grain boundary diffusion and grain boundary restructuring are widely used as approaches, which allow one to improve hysteretic properties of Nd-Fe-B-based magnets, namely, to enhance the coercivity and reduce the heavy rare-earth consumption of Nd-Fe-B sintered magnets simultaneously. Some progresses have been made in efforts to introduce heavy rare-earth metals (REMs) in the form of hydrides. In recent years, permanent magnets based on (Nd,Pr)2Fe14B compound are of interest for investigators owing to the possibility to use these magnets at low and cryogenic temperatures. In contrast to Nd2Fe14B compound (at 135 K, its easy-magnetization axis anisotropy changes to easy-axis cone anisotropy), the Pr2Fe14B compound does not undergo the spin-reorientation transition, and the natural increase in the hysteretic parameters with decreasing temperature can be adequately used. In the present study, we investigate the effect of HoH2 hydride addition on the hysteresis loop parameters of sintered Pr-Fe-Ti-Al-Cu-B magnets. The magnets were prepared by traditional powder metallurgy technology, and 3 wt. % HoH2 was added to the powder at the fine-milling stage. The magnets demonstrate the monotonic increase in all hysteretic parameters with decreasing temperature up to 4.2 K. The structure of the magnets was studied in detail by scanning electron microscopy (SEM/EDX), and the formation of so-called &quot;core-shell&quot; structure was demonstrated, which is assumed to favor the marked improvement of hysteretic properties of Pr-Fe-B-based magnets. The coercive force and maximum energy product at 4.2 K are Hc = 5420 kA/m and (BH)max = 352 kJ/m3, respectively. Domain structure of the magnets was studied perpendicular and parallel to the magnet texture using magnetic force microscopy. The data obtained indicate the well-formed magnetic texture. The average domain width is 1.2-1.8 um.

Czech name

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Czech description

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Type

O - Miscellaneous

CEP classification

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OECD FORD branch

20501 - Materials engineering

Project

<a href="/en/project/LTARF18031" target="_blank" >LTARF18031: Development of physico-chemical and engineering foundations for the initiation of innovative resources-economy technology of high-power and high-coercivity (Nd,R)-Fe-B (R = Pr, Tb, Dy, Ho) low-REM permanent magnets</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2018

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů