Low-cost Ce1-xSmx(Fe, Co, Ti)12 alloys for permanent magnets

Abstract

Ce1-xSmxFe9Co2Ti alloys based on the ThMn12-type crystal structure have been synthesized via melt-spinning of prefabricated alloys and via mechanochemical processing of CeO2- Sm2O3- Fe2O3-TiO2- Co - Ca - CaO powder mixtures. Coercive fields up to 0.8 kOe and 2.1 kOe were obtained in annealed melt-spun alloys with x = 0 and x = 0.5, respectively. Submicron, partially anisotropic particles collected after the mechanochemical synthesis for x = 0.5 and x = 1 exhibited coercivity (energy product) of 1.8 kOe (5.4 MGOe) and 5.8 kOe (9.9 MGOe), respectively. The low magnetic anisotropy field of CeFe9Co2Ti alloy requires at least a partial Sm-substitution for Ce in order to develop a reasonably high coercivity.

Mechanochemical Synthesis and Nitrogenation of the Nd1.1Fe10CoTi Alloy for Permanent Magnet

“…A temperature of 1000 • C was found to be optimal for the formation of the ThMn 12 -type structure. For nitrogenation, the annealed powders were sealed in quartz capsules under 80 kPa of a 99.999%-pure N 2 and held at 350 • C for 3, 6, 9 and 12 h. Finally, a multistep procedure of repeated washing with deionized water, glycerol, acetic acid, and ethanol [19] was used to collect the ferromagnetic nitrogenated particles, and to remove the CaO, rare earth oxides and unreacted Ca.…”

“…No significant coercivity, however, could be developed in the NdFe 11 TiN x compound, which is particularly attractive due to the high M s of 1.48 T [17]; even the µ 0 H c reported for the nanocrystalline alloys did not exceed 0.23 T [11]. The mechanochemical synthesis was demonstrated to yield single-crystal submicron and nanoparticles of hard magnetic materials, including the R(Fe,M) 12 alloys, which exhibit coercivity values typical of nanocrystalline powders [18,19]. This synthesis technique also requires less-expensive oxides, rather than metals, as the raw materials, and it may be expected to reduce local demagnetization fields due to more regular shapes of the particles [20].…”

Bayesian optimization of chemical composition: A comprehensive framework and its application toRFe12-type magnet compounds

“…RFe 12 -type compounds having the ThMn 12 structure have been considered as a possible main phase of a strong hard-magnet because they are expected to have high magnetization due to its high Fe content, and to have high magnetocrystalline anisotropy if the R element is properly chosen. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] The magnetic properties of NdFe 12 N was evaluated theoretically a few years ago [38], and its high magnetization and anisotropy field were confirmed by a successful synthesis of NdFe 12 N x film. [39,40] Unfortunately, NdFe 12 N and its mother compound NdFe 12 are thermally unstable.…”

Mechanochemical synthesis of magnetically hard anisotropic RFe10Si2 powders with R representing combinations of Sm, Ce and Zr

“…The mechanochemical synthesis (a reduction-diffusion of mechanically activated precursors) of high-H a compounds has been shown [20] not only to produce H c values comparable to those in nanocrystalline materials, but also to yield anisotropic, often single crystal particles with the theoretical (BH) max approaching that of the compound. Indeed, a superior (BH) max value was recently obtained in submicron Sm(Fe,Co,Ti) 12 particles prepared this way [21]. Somewhat larger Nd(Fe,Mo) 12 particles prepared via reduction-diffusion of chemically synthesized 3 precursors showed a noticeable H c after subsequent nitrogenization [22].…”