“…This gradient distribution indicates that the matrix phases contain various Ce-containing grains. Moreover, the magnitude profile of Ce in the matrix phase shows that there is penetration of Ce from the grain boundary into the (Pr/Nd)–Fe–B (alloy I) grains during the sintering process and an obvious core–shell structure is obtained for the DMP magnet 5 , 6 , 20 . Figure 2 BSE-SEM images of the DMP magnet ( a ) and SP magnet ( b ).…”
Section: Resultsmentioning
confidence: 99%
“…From commercial standpoints, less expensive and more abundant isostructural compounds with similar magnetic properties are always desired, so various isostructural Re 2 Fe 14 B compounds have been investigated and their properties analyzed [2][3][4] . In particular, the large backlog and inexpensive Ce-based magnets are currently research hotspots [5][6][7][8][9][10][11] .…”
The high coercivity of Nd–Fe–B magnets can also be obtained in the Ce–Fe–B magnets fabricated via the dual-main-phase (DMP) method in which the high abundance Ce was used to substitute Nd(Pr). The inhomogeneous distributions of the matrix grains in the DMP magnet play a key role in the enhanced magnetic performance. Compared with the single-phase magnet, more grain boundary phases encapsulating the matrix 2:14:1 grain are formed in the DMP magnet, which reduce the exchange coupling between adjacent magnetic grains. The switching field distribution and the interaction field distribution of the Ce–Fe–B magnets were determined by the first-order-reversal curves (FORC). The switching field peaks around 6 kOe, 11 kOe and 12 kOe in the FORC distribution indicate that three major reversal components coexist for the DMP magnet. The overlapp of the second and third switching field peaks reveals the presence of a pinning interaction within individual magnetic grains with a core–shell structure, which further improve the coercivity of the magnet.
“…This gradient distribution indicates that the matrix phases contain various Ce-containing grains. Moreover, the magnitude profile of Ce in the matrix phase shows that there is penetration of Ce from the grain boundary into the (Pr/Nd)–Fe–B (alloy I) grains during the sintering process and an obvious core–shell structure is obtained for the DMP magnet 5 , 6 , 20 . Figure 2 BSE-SEM images of the DMP magnet ( a ) and SP magnet ( b ).…”
Section: Resultsmentioning
confidence: 99%
“…From commercial standpoints, less expensive and more abundant isostructural compounds with similar magnetic properties are always desired, so various isostructural Re 2 Fe 14 B compounds have been investigated and their properties analyzed [2][3][4] . In particular, the large backlog and inexpensive Ce-based magnets are currently research hotspots [5][6][7][8][9][10][11] .…”
The high coercivity of Nd–Fe–B magnets can also be obtained in the Ce–Fe–B magnets fabricated via the dual-main-phase (DMP) method in which the high abundance Ce was used to substitute Nd(Pr). The inhomogeneous distributions of the matrix grains in the DMP magnet play a key role in the enhanced magnetic performance. Compared with the single-phase magnet, more grain boundary phases encapsulating the matrix 2:14:1 grain are formed in the DMP magnet, which reduce the exchange coupling between adjacent magnetic grains. The switching field distribution and the interaction field distribution of the Ce–Fe–B magnets were determined by the first-order-reversal curves (FORC). The switching field peaks around 6 kOe, 11 kOe and 12 kOe in the FORC distribution indicate that three major reversal components coexist for the DMP magnet. The overlapp of the second and third switching field peaks reveals the presence of a pinning interaction within individual magnetic grains with a core–shell structure, which further improve the coercivity of the magnet.
“…It is hard to obtain pure 2 : 14 : 1 phase in the CeÀ FeÀ B-based alloy by the reason of the unavoidable existence of REFe 2 phase [19]. The proportion of RE 2 Fe 14 B phase diminished due to the generation of REFe 2 phase, leading to the magnetic properties deterioration in the sintered magnets [20]. Stronger 2 : 14 : 1 phase diffraction peak with weaker REFe 2 phase diffraction peak can be observed in the (La 0.35 Ce 0.65 ) 17 alloy.…”
Section: Phase and Microstructure Evolution Of Strip Cast Alloymentioning
In this study, lanthanum was applied to strip cast CeÀ FeÀ B alloy to improve its phase composition and microstructure. The results reveal that lanthanum doping can significantly enhance the proportion of 2 : 14 : 1 phase and improve the microstructure of CeÀ FeÀ B alloy. Besides, the influence of the starting alloys structure on the microstructure and magnetic properties of final multi-phases cerium-containing magnets was also systematically investigated. Compared to the multiphases magnet without lanthanum addition, a pronounced coercivity increment could be distinguished in lanthanum-doping multi-phases magnet, which could be attributed to the finer grain size together with ideal grain boundary. In this work, the superior performance of H cj = 701.28 kA/m B r = 1.30 T, and (BH) max = 313.70 kJ/m 3 were obtained by blending NdÀ FeÀ B alloy with (La 0.35 Ce 0.65)-FeÀ B alloy to meet 25.0 wt.% lanthanum-cerium utilization content, suggesting that the possibility to develop high abundant rare earth permanent magnetic materials.
“…1) but also in most published works [13 -20]. Unfortunately, only few authors discussed the possible role of GB oxide layers in Nd-Fe-B-based permanent magnets [21][22][23][24][25][26][27][28][29][30]. Partially, it is because the experimental possibility for the reliable local measurements of oxygen content using electron energy loss spectroscopy (EELS) with simultaneous determination of oxide phase crystal structure by means of high-resolution TEM (HRTEM) is not always available.…”
In this review we consider the microstructure of grain boundaries (GBs) in the Nd-Fe-B-based alloys for permanent magnets. It is generally accepted that the unique hard magnetic properties of such alloys are controlled by the thin layers of a Nd-rich phase in Nd 2 Fe 14 B / Nd 2 Fe 14 B GBs. These GB layers ensure the magnetic isolation of Nd 2 Fe 14 B grains from each other. It is generally supposed that such GB layers contain metallic Nd or Nd-rich intermetallic compounds. However, the commercial Nd-Fe-B-based permanent magnets frequently contain the tangible amount of neodymium oxide Nd 2 O 3 in the triple junctions between Nd 2 Fe 14 B grains. In this review we show that oxide layers are also present in the GBs in Nd-Fe-B-based permanent magnets. The Nd-based phase in GBs can form continous layers between Nd 2 Fe 14 B grains (this case is called complete wetting). It corresponds to the zero contact angle between GB and Nd-rich phase. If the contact angle is non-zero, the Nd-based phase forms the chain of particles in the GB. In turn, if the GB between these particles is "dry", this case is called the incomplete wetting. If the GB between the Nd-rich particles contains the thin layer of a Nd-rich phase (either metallic or oxide), this case is called the pseudo-incomplete (or pseudo-partial) GB wetting.
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